I recently replaced the screen on my MacBook Pro (for the 2nd time). During reassembly, I could only get 2 out of the 3...

Also, make sure you're using a charger with sufficient power rating - 12W is what was supplied with the iPad Pro 9.7". https://support.apple.com/en-us/120548. A lower wattage charger will either charge very slowly or not at all.

I'll preface my response with "This could be for many reasons and my info might be way off the mark". Most likely, you've got a runaway process/application (or more than one) that is chewing your computer's resources (CPU,Memory,Disk,Network). I would check this using the Monitor utility (Applications/utilities/Monitor). This will let you see if you have a CPU bottleneck i.e CPU Load ~100%; or Memory is a bottleneck i.e Memory Pressure is NOT GREEN (i.e. amber or red); or your disk is a bottleneck Disk IO is high (Read in/sec; Write out/sec). If you can see that CPU, Memory or Disk is over-utilised; then use the process list to sort by '% CPU' for CPU overload; sort by 'Memory' for memory bottleneck; sort by Bytes Written or Bytes Read for disk bottleneck. Take a look at the top entries in the process list to identify which App or Apps are the culprit and then go to the apps and quit them. So, a few other things to think about: (1) Low 'free space' on disk - this will slow things down - the fix is to...

That wattage might be low for an iPad Pro 9.7" - see here for details on the supplied chargers for apple devices - which indicates the supplied adapter is rated for 5watts. 2x possibilities I can think of: (1) The charger is not putting out enough current to charge the battery - use the original iPad charger (or any USB charger that rated for at least 5watts) (1.1) The battery is dead and not accepting a charge; in which case a replacement is likely best option. Can probably find a repair shop if you're not confident to do it yourself - or if you're up for it there's a repair guide here