Re: Imessage does not work on iphone 17 pro
If you recently updated the iOS version:
After a major upgrade, like iOS26, there is often a lot still happening, re-indexing etc., going on in the background to complete the update process and to have everything working smoothly ... often seems best to keep iPhone well-charged and give things time to complete.
You may want to check whether you have low-power mode on or not.
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Else:
First, if you haven't already: try re-starting your iPhone
If you still need help:
Check for interference issues with your Apple communication apps.
Eg: If you use third-party (non-Apple) apps on your iPhone:
Unnecessary apps like ad-blockers, virus checkers, cleaners and the like (even VPN) often cause issues.
If installed, you can try turning them off (or use uninstallers from their developers) to see if that helps.
If you use a "block junk-callers" type of third-party app, ensure there are not excessive amounts of "blocked" or "junk-caller" contacts listed.
Out-of-date browser extensions can also cause issues ... turn off / uninstall / or update if possible.
Any third-party apps you find necessary may need updating in order to remain compatible, and not cause issues: