VPN App 'Update Required' issue

I'm building a VPN app with Flutter, and I'm coming across this issue(only on iOS) - "${appName} must be updated by the developer before ${appName} can be connected."

I have checked and tried almost all the solutions on the internet, but none work. Can anyone who has encountered this before assist or point me toward resources that can help?

VPN App 'Update Required' issue
 
 
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