Sms from Pixel 4 to 1 person's iPhone stopped working

[Smsfail42]

I can't text and sms message to a person I've texted all the time, in fact just yesterday. Now it says message not sent, tap to try again. This is from my Google pixel 4 xl to his iPhone. I'm using the default Google Messages app. It happens on both wifi and LTE. MMS will go through though. I also can receive both sms and mms from him. I had this happen about 6 mos ago with a different person (iPhone)and it resolved itself after about 3 mos. I also had it happen a month ago with yet a different person (iPhone) and after I deleted the text conversation and then it worked. I'd prefer not to delete the text conversation with people when this happens. Tried VZW for help and got no help in fixing...restart, update software, clear cache, none of that worked.  Help.

[vzw_customer_support]

Hello, we can look into this for you. Please send us a Private Note to continue.