Many users on the old chatterboxtown.us service are seeing this error in the Cheogram Android app. This was caused by a failed upgrade on chatterboxtown (the admin has said the intend to retry the upgrade). For now this is the instruction to bypass the error:

In the “manage accounts” screen, tap on the account name (not the toggle switch, the account name). That takes you to the “account details” screen where you will find the “accept” button. Tap “accept” and that should let you log in.

For JMP customers: remember, if you prefer you are always welcome to contact JMP support and switch over to the Snikket instance you pay for with your JMP account.