The AEDT integration is based on optiSLang calling AEDT and feeding it scripts to execute. So here there are generally the two Python scripting layers involved, the IronPython runtime in AEDT and the Python layer of the AEDT integration within optiSLang.
Check error messages in the main message log of optiSLang. Concentrate on the error having occurred first.
Check all messages in the main message log of optiSLang because the AEDT integration scans for error and warning messages stemming from AEDT and lifts them up into the optiSLang message log where they can only appear without coloring as neutral log messages. Normally, these messages are at least easy to spot because they start with either [WARNING] or [ERROR].
Check the various log files produced depending on the run mode.
Relevant files and their location: all log files of nonzero kilobyte size appearing in design directories.
