The court shall reinstate the case upon finding after a hearing that the failure of the party or his attorney was not intentional or the result of conscious indifference but was due to an accident or mistake or that the failure has been otherwise reasonably explained.
In the event for any reason a motion for reinstatement is not decided by signed written order within seventy-five days after the judgment is signed, or, within such other time as may be allowed by Rule 306a, the motion shall be deemed overruled by operation of law. If a motion to reinstate is timely filed by any party, the trial court, regardless of whether an appeal has been perfected, has plenary power to reinstate the case until 30 days after all such timely filed motions are overruled, either by a written and signed order or by operation of law, whichever occurs first.
Tex. R. Civ. P. 165a