Just added a 4th quarter payment using test desktop and online returns with no issue.
If you are using the TurboTax online editions, sign out of the tax return. Close the web browser window for TurboTax.
Clear cache on your web browser - https://ttlc.intuit.com/community/troubleshooting/help/how-to-clear-your-cache/00/26135
Sign back onto your TurboTax online account - https://myturbotax.intuit.com/
See if the problem has been corrected.
