Group texts no longer received by groups with both Apple-Android users; no failure notice

Am at my wits end. About 10 days ago, my texts in groups that are iPhone-Androids show that that my texts successfully sent via SMS. Yet, they are not received, and I don't get a "fail to send" notice. I receive other members texts in the group. At that time I had a two-year-old iphone 13Pro. Manually dated software to 17, then 18 (even though auto was turned on, that did not happen; no alert that a software update was available.) Spent hours in person in Apple, on phone with Apple, and on phone with T-Mobile. After going through their check-downs (hardware and software diagnostics, toggling RCS on and off, turning off and on iMessage, MMS, SMS, RCS, deleting one of the groups, hard restart), I did a factory reset. No difference. I bit the bullet and got a new device, the 16Pro. NO DIFFERENCE! Did the new device just import the messaging problem? If so, what is it? Thanks in advance.