Collect the log bundle from 7-MTT, in the log bundle you will have your projects and the folder "PRECHECK". Check the log files in there and look for the error entry this will tell you more in WHY it fails.
Im my experiance, in most cases it is related to still running "import" jobs on the destination cluster which prevents the precheck from completing.
Anyway, if you need a analysis open a CASE so tech support can go over the 7-mtt log bundle.
We are using 7MTT version 3.3 and we have the same problem. I have gone through the troubleshooting steps which you have mentioned here but still issue wasn't resolved. So could you please help us here.