Glad that you didn’t have to wait too long, and apologies for the frustration you’re encountering.
If users of your application are seeing error code 326 (or that message is being surfaced to your application) then it usually means that unusual behaviour is being detected on those accounts, possibly due to automation which violates the policy and rules. The behaviour would then be for the account to be locked or temporarily restricted until the user visited their profile on Twitter.com to unlock the account. This is not necessarily related to your app - something else may have caused this. If you’re finding that every user is affected, then it is possible that something your app is doing is related, but that’s not definitely the case.
Some of our user safety and antispam systems may cause this to happen based on behaviour detection, and since this is algorithmic and adaptive it not possible for us to list out every scenario that might trigger the rule. There’s some additional information in this support article.
