ul problem

hello
I keep getting this message on phone and now messages won't send. The message is as follows:
System UI not optimized for the latest version of Android" error.

it started last night and internet kept going off I called provider and they said its all good now but they didnt do anything to help with the error message. I can use email, search ect but not messeger. I cannot send or receive messages.
Thank you so much I havent been in here in a very long time. Your always such a help

What is the make/model of the phone? Have you checked to see if it has the latest available operating system updates and/or updating manually? What are you doing when that error message appears? Is it Facebook messenger you're using?