Macbook Pro (mid-2012) battery not identified (shows X) after SSD install I recently upgraded my MacBook Pro (mid-2012) HDD to SSD.
Once SSD install was complete, my macbook did not start, however when plugged into power, it started booting, and worked normally.

The battery was in decent condition, and was always lasting 3+ hours.

I tried SMC reset, and PRAM reset few times in last few days, however no change in status. On removing the power adapter, it goes to sleep mode.

Very annoying that now onwards, I always have to plug in the power for doing any work.

Any potential hints ...
Based on what you’ve described, it sounds like you may have accidentally damaged something internal during your upgrade. Since Apple Hardware Test didn’t turn up anything, ordering a replacement battery is a reasonable next step. If that doesn’t work, then there must be damage to the logic board. You can get tested replacement boards for around $200 or so on eBay.