This is due to the HMRC credentials entered in the software not matching those held at HMRC.

First step is to check you credentials with HMRC work as expected, to do this go to HMRCs website and login to the tax account to ensure they work.

Next step is to check the HMRC credentials within SA Submission Pro you need to open the software and then go to FBI>FBI Sender information, update these credentials to ensure they match those used to login to HMRCs website.