First Option

Please try to reset the Twilio number and see if that works.

Second Option

If not, please follow the steps below and see if the webhook URL for SMS is set up properly?

Go to the top right -> Click Account -> Click Subaccounts

Search based on the Twilio Subaccount SID in HighLevel agency settings -> Twilio

Click into the subaccount
Once you are in the subaccount, it should show the yellow highlighted subaccount name on the top left

Check if the Twilio number is configured properly
Go to Develop on the left menu
-> Explore products
-> Scroll down to find Phone numbers

Click Phone numbers:

Check if it is configured as:

Voice: https://msgsndr.com/twilio/incoming_call
Messaging: https://msgsndr.com/twilio/incoming_message

OR

Voice: https://api.gohighlevel.com/twilio/incoming_call
Messaging: https://api.gohighlevel.com/twilio/incoming_message

Either is fine.

If not, please click the phone number and scroll down to replace the webhook: