A. Clear the app's cache and data. Go to Settings > General > iPhone Storage, find the VPN app, and select 'Offload App' to clear temporary files without deleting your data. Then, reinstall the app from the App Store if necessary.

B. Check for any additional updates. Sometimes, a subsequent update is released to fix bugs from the previous version. Go to the App Store, tap on your profile icon, and scroll down to see if there are updates available for the VPN app.