I've filed about 100 returns already this season and just started having my returns rejected for:

"The EFIN used to transmit this return is not a registered EFIN with the IRS or may not be registered to transmit this return type. Verify that your EFIN has been accurately entered in ProSeries by going to Tools, Options, and Firm/Preparer Info. Make corrections if necessary, then reopen and save the return prior to resubmitting. If it is necessary to review or update your EFIN, copy and paste this web address in an internet browser to go to IRS e-Services where your EFIN can be updated online."

Why would my EFIN suddenly start being rejected?