User access changed but user not able to access on app

I know some troubleshooting steps to help fix the issue, Penlew.

Sometimes, the app has a large amount of data, resulting in odd results. Consider telling your user to clear the app's cache to resolve the problem.

To clear the cache in your QuickBooks Online app, you can follow the steps below:

• Android - Select the Menu at the bottom and click the Settings icon. Then pick Refresh Data and choose Yes.
• iOS - Tap the Menu at the bottom and click on Help & Feedback. Then select Refresh Data and Refresh.

To clear cache in your phone settings:

• Android - Select Apps from your phone's Settings (varies by device). Choose the QuickBooks app from the list and pick Storage, then Hit Clear data.

• iOS - From your phone's Settings, choose Settings. Click on General and choose iPhone Storage. Select an app that's taking up a lot of space. To free up the Storage without deleting the documents and data for the app, select Offload App.

I recommend checking these articles for more details on troubleshooting the QB Online app:

•  Fix common errors in the QuickBooks Online mobile app for Android.  
• Clear cache and cookies to fix issues when using QBO.

Let me know if there's anything else I can do to help. Thanks!