VoLTE user stuck in 2G in good LTE radio conditions

4G LTE
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Hi Experts.

Any idea why VoLTE user stuck in 2G in good LTE radio conditions?

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Could be anything ranging from TAU reject in LTE to no EARFCN info in SI2Q 2G.

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What should I need to check?

Majorly this happening on other MNC number.

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Check SIB2Quatr in 2G whether it has EARFCN info.

Check NAS if there was any undesired TAU rejects or EMM rejects like #15 or #19.

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Yes undesired reject was there.

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Then you have the reason :+1:t2:

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But I didn’t find when customer goes to 2G why it doesn’t come back to LTE.

Why it needs to fresh LU.