Solution for OnePlus 3 dual sim 'No Network' issue created a huge problem as i had Reliance Jio 4G sim and 2nd Sim wasn't getting detected with that. I found many users complaining regarding this issue. I had same issue, may be the second sim isn't supported with higher network band like 4G. You need to switch sim2 network to 2G. I have one VoLTE supported (JIO) sim1 and another 4G LTE (!dea) sim2. Network on sim2 was showing 'No service' error. This is what I did. Video https://youtu.be/pdb1GT2Wv4s I turned off my sim1 and sim2 started getting network. Go to cellular network in setting (kept sim1 off), tap on SIM2 tab and under Preferred Network type switched to 2g, wait for network to arrive on sim2 then turned the sim1 ON. Luckily both Sims working now ;) For some reason, the sim2 gets switched to 4G again but doing same steps does the job again. Good luck.
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