Why my text message not working again

Optimize the range of the mobile network, see this Apple article:

If you see No Service or Searching on your iPhone or iPad

If you see No Service or Searching on your iPhone or iPad - Apple Support

See also -> If you can't send or receive messages on your iPhone, iPad, or iPod touch

If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

See if anything here helps

An older article, but see if the troubleshooting helps.

Handoff Continuity Troubleshooting.   -

iPhone, iPad, iPod touch, and Mac using Continuity - Connect.    *

How to forward text messages on your iPhone.   *

SMS Relay - Set up and use –Yosemite/ iOS 8.   -

SMS Relay - Set up and use –Yosemite/ iOS 8  (2).  -

Text messages forwarding.   -