With new version TAS (6800 and later) and new version TRB (3788 and later), you cannot import each other’s project files directly. To open TRBC projects with TASC, please follow the steps below.
Open the affected TRBC project, go to Start > Options > Tick Save model files when projects are saved.
Save as > Replace the original project file.
Go to TASC > BIM MODEL > Import TRB Model, now you will be able to import TRBC project into TASC.