It is usually good practice to identify your operating system and Shotcut version when asking for help (at a bare minimum). Also, please attach the log file (view → application log) and the project mlt that is failing (use the upload button to attach these when composing your reply).
I’m going to assume Windows at this stage, so make sure when you do the reinstall, you follow the below procedure exactly, especially since that poster had the same export issues as you.