Import from TMX into server TM does not show how many "invalid" entries were found. Unlike in Studio where you get detailed information about the number of entries imported and the number of errors, this info is not available in GS.
That leads to an awkward process where you may have a large number of error entries (and you don't know how many). You will have to look at each entry in the error-export file to try and fix it, reimport, wait for success or failure and repeat the process again.