EMM cause (LTE NAS)3GPP TS 24.301 §9.9.3.9 and Annex A
What it means
No EPS bearer context activated: the network has no active bearer for the phone (e.g. it lost the context).
Where you see it
In LTE NAS Attach reject, Tracking area update reject, Service reject or Detach request.
What to check
Usually followed by a fresh attach; check for context loss in the MME/SGW if frequent.
Look at the S6a (MME↔HSS) and S11 messages just before the reject: they usually show the real trigger.
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