USA-based acct | 2287 Users | 3800 DID lines | 28 sites | all Polycom VVX500 phone handsets
2019-09-20 Please verify for sure, Via web browser or an RC App? In your post, you said App, but many folks confuse and actual software APP with the regular web accessed Service Web portal.
Please clarify. And if you are using an App --- which actual app are you using and what version of that app?
If web browser, update your web browser to most current rev and make sure you have already cleared your Browser Cache and Cookies.
If you have Administrative access to your RingCentral Service Web console. the Audit log will shed some light on what is a possible cause of your login error message.
Same info for App access - the Service Web Audit Log will indicate what the possible issue is with your Login error.
Join our unofficial RingCentral Admins User Group
http://ringcentraladminusersgroup.org/index.html