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I used to receive a 5G signal in supported areas (in my office) and at the pub. However, I can no longer pickup the Vodafone 5G network wherever I am, even when the coverage checker says I should be able to.
I have a Samsung S20+ 5G, which is unlocked and receives 5G correctly on other networks.
If your phone is getting 5G using other networks then that points to the phone being probably not at issue.
Ask customer services to check your account to ensure 5G is still activated.
Maybe as a process of elimination try your sim card in another phone.
In my opinion 5G is still in it's infancy and can be a little hit and miss.
I wish you all the best with this situation.
Current Phone > Samsung Note 20 5G - SM9860 Snapdragon.
Samsung One Ui 2.5 / Android 10.
Thanks for replying.
It all used to work ok, so it points to there suddenly being a problem with my account from nowhere! 5G does show as correctly enabled.