Kelsey, J.

Shaib Y. Rios of Brock & Scott, PLLC, Fort Lauderdale; Kimberly S. Mello and Vitaliy Kats of Greenberg Traurig, P.A., Tampa, for Appellant.

No appearance for Appellees.

Kelsey, J.

The final judgment on appeal denied Bank of New York Mellon's foreclosure complaint because the trial court sua sponte concluded that the note in the court file was a copy rather than an original. Appellees had asserted no affirmative defenses. They did not deny being parties to the note and mortgage, did not challenge the note's authenticity or the bank's standing to foreclose, and did not object to the note at trial. The bank thus had no advance notice of what turned out to be the dispositive issue. Both at trial and in a timely post-trial motion, the bank requested leave to amend and bring in a new witness on authenticity. The trial court denied both requests. We reverse and remand for reinstatement and resolution of the foreclosure action.

I. Facts.

The bank's sole witness, a loan analyst, testified that the note was "either a copy or the original of the promissory note." The trial court gave the borrowers a chance to state any objection to the note, and aside from saying they had been dealing with a different entity (the loan servicer), they stated no objection. The bank's witness then proceeded with the typical information about payment history and so forth.

When the bank's witness finished testifying, the court questioned whether the note was original, noting that a prior foreclosure action was settled and the original loan documents were released. The bank's counsel explained that the note bore an original recording stamp, which coincided with the return of the note upon settlement of the earlier foreclosure action, and established the document as an original.

The trial court, however, thought the note was a copy because it had a fax header, parts of the document appeared to be copied, and the borrowers' signatures were in black. Counsel again explained that it more than likely was faxed to the title company for execution, that the clerk of court required black ink signatures at that time because scanners could not pick up blue ink very well, and that the original recording stamp established originality. The loan analyst offered to re-examine the document and testify specifically about its indicia of originality, but the trial court cut off the witness and announced that the bank had not proven its case and foreclosure was denied.

The bank's counsel immediately orally requested leave to address the issue in an amended complaint and potentially with a new witness to authenticate the note. The court denied that request. In the subsequent written order denying foreclosure and closing the case, the court repeated the points made at trial, and added new "findings" of fact about characteristics of the note.

The bank timely moved for rehearing or new trial. The bank argued that any question about whether the note was original was waived because the defendants had not asserted any affirmative defense or otherwise questioned the note's authenticity or the bank's standing, and as a result the bank had no prior notice of any issue about the note. The bank also asserted that it had retained a documents expert who could testify that the note in the court file was an original.

The trial court denied the bank's motion, explaining what led to the conclusion that the note was a copy. The court rejected the bank's waiver argument on the grounds that the court as the trier of fact had the authority to decide whether the note was original. This appeal followed.

II. Analysis.

While the trial court correctly summarized the court's authority to resolve questions of fact in a bench trial, the analysis incorrectly skipped the threshold requirement that a party must first raise the legal issue to which the facts relate. See Haycook v. Ostman , 397 So. 2d 743, 744 (Fla. 5th DCA 1981) (holding that a prima facie case is made when a facially sufficient note is filed, and thereafter "[a]ll attacks upon [a promissory note] ... must be made by way of affirmative defenses"); Fla. R. Civ. P. 1.140(h)(1) (providing defenses and objections are waived if not made by motion or responsive pleading). A party's failure to raise an argument is a waiver. Johnston v. Hudlett , 32 So. 3d 700, 704 (Fla. 4th DCA 2010) (holding objection to authenticity of loan document was waived due to lack of contemporaneous objection). The trial court erred in raising and ruling on an objection and arguments the defendants did not assert.

The court is not authorized to become a party's advocate and raise a legal issue sua sponte. See DiGiovanni v. Deutsche Bank Nat'l Tr. Co. , 226 So. 3d 984, 988 (Fla. 2d DCA 2017) (holding that trial court must maintain neutrality and cannot become a participant in proceedings, and exceeded its authority in independently investigating facts); Connelly v. Matthews , 899 So. 2d 1141, 1143 (Fla. 4th DCA 2005) (holding, where trial judge raised issue no party had raised about note, "The role of trial judges does not allow them to become advocates for one side or the other, and especially not in a nonjury trial where the judge is the decider of the claims and defenses of the parties"). The trial court erred in raising and ruling on the basis of arguments the defendants never raised.

Even if the defendants had raised these issues for the first time at trial, it would be an abuse of discretion to deny the bank any opportunity to amend and present additional evidence. See Hernandez v. Cacciamani Dev. Co. , 698 So. 2d 927, 928–29 (Fla. 3d DCA 1997) (reversing trial court's order denying rehearing, as abuse of discretion, where holder of note demonstrated it could provide the original). The interests of justice heavily favor allowing additional evidence under these circumstances. See Grider-Garcia v. State Farm Mut. Auto. , 73 So. 3d 847, 849 (Fla. 5th DCA 2011) (finding abuse of discretion and reversing order denying motion to reopen for authentication of policy document, where omission was inadvertent and a single witness could resolve the issue).

We reverse the judgment and remand for further proceedings consistent with this opinion.

REVERSED and REMANDED .

Ray, C.J., and Winokur, J., concur.