This issue typically happens when the app updates and accidentally loses the ' wi fi token'. Please follow the steps below to resolve that issue. If it does NOT fix the issue, please let me know.
RE- RESET WIFI
To reset wifi texting: turn data ON. Launch Verizon Messages> Main Menu> Settings – under Integrated Messaging , select 'Unsubscribe'. Wait a few seconds. Then re-'Subscribe' to Integrated Messaging. Once you receive and activate the security code, select ‘Restore messages’ in Main Menu and then turn off data to use wifi.