Suddenly stopped getting verification texts

Without warning, I suddenly stopped getting two-factor verification texts from many senders on my phone and also in my Messages app on my computer (iPhone 14 with current software, iMac with current software). I did change Verizon plans about a month ago, but everything worked fine after that for several weeks before this problem began. This could be a Verizon problem, I recognize, but the horror of having to deal with their small business division leads me to ask the community here at Apple first.

I have had to revert to e-mailed codes in some cases, and in some cases I have been unable to access accounts or verify transactions because the text message simply never came. Services affected include PayPal, American Express, and others, though some seem to work fine.

This is a major problem in functionality, and to have it crop up without warning is extremely problematic.

It's possible that I mistakenly hit "this is junk" for such texts from some accounts because of the new (and fortunately, quick reversed) "feature" Apple imposed of having to do yet another click to delete a text by saying whether it was junk or not. When this feature was active, the "This is junk" button was where the "Yes, delete" button had previously been for texts on my phone, so it was easy to hit it by mistake. (Apple, clearly intentionally, makes it ridiculously hard to delete text messages, requiring multiple taps/clicks for each individual message, for some reason, but that's a different beef).

Thanks in advance for any support. (I have done the usual things: restarted the phone, etc. Also note: these texts ALSO do not arrive on my Mac, though many verification texts used to arrive there too.)