I bought a Nexus 5 on Ebay. It came brand new with all the packaging, but having bought a previous Nexus 5 (directly from Google) this packaging seemed a little suspect (I think it might be a very well made imitation, or a modified LG version of the device. Seemed legit on the website though).
Anyhow, when it arrived i put in a local SIM, but it wouldn't connect to the cellular network, or it would connect intermittently (5-10 seconds and it would drop off). I went into the settings and noticed that the IMEI read '0'. It was on Android 4.4.4.
It seems that if the IMEI is 0, the device would fail security checks (either with the MEID or the IMEI zeroed) and thus not register on the network.
After Googling quite a bit, I came across these answers on StackExchange, however they're not entirely clear: Nexus 5, IMEI 0, how to restore IMEI? (Refers to a Russian website, and you need to translate to English ... so it's kind of messy) https://android.stackexchange.com/questions/96397/nexus-5-imei-0-shows-how-to-restore-original-imei
None of these was actually clear and after quite a bit of fumbling about, nothing seems to have worked. So how does one get this fixed?