TMobile has just released an update about their 5G and issues with SIM cards. They have found that customers whose SIM cards have the letters TM plus 4 numbers are not 5G compatible. The new compatible SIM cards have R15 on them and are compatible. If you have a non compatible SIM card and have a 5G phone, please reach out to TMobile for a new SIM card.
Hope this helps with the 5G connection issues, as I found that my SIM card wasn't a compatible one so I will be stopping at my local store for a replacement.
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