Hi there,
Automatic transmissions are extremely complex item, the light may well have set a fixed fault code in the ECU. Have that checked, as for the reason for your transmission error, this type of issue would be best discussed with your dealer, i have not experienced this problem in your type of car before, but your dealer may well have a past history and should be able to advise you on what needs to be done, but the very first thing is to have any transmission codes read, as this will be the first place to find any indication of a problem.
Mark (mhpautos)