Battery still says 'Replace Now' even after a new battery + I/O board

Hi!

Ok, So I was having issues with my Macbook Pro 2015 retina display 13 inch running on the latest version of Catalina 10.15.4 where the battery died so I got the status 'Replace Now', 'Battery Not Charging' and all of that. So ofc it would only work on the power adapter and if I took it out it would shut down immediately. So ofc to save myself hundreds I bought what I needed and attempted to fix the issue myself. The first thing I did was buy a new battery. After installing the new battery and doing an SMC reset, same status, same issue, no change.

I then came across this article: ++New battery is not charging and condition says replace now? It mentions that if this issue occurred the guy at the shop would recommend replacing the I/O board (btw I know this is for a 2011 macbook air, But I found a guide for a 2015 retina macbook pro and followed it and did exactly what it said). So yeah surprise surprise after buying a new I/O board now and replacing that and doing an SMC reset, again same issue.

I have heard that with a new battery you need to calibrate it, however, I can't do that as that requires disconnecting the power and the computer just shuts off this way so it's not an option. The battery cycle count is currently 0 cycles however the battery health reads as 100% on 'coconut battery health'

I'm fast running out of ideas... and the will to live and I'd really rather save myself hundreds of pounds and not take it to a repair shop as I’m very capable of doing it myself if I just know the issue and how to fix it. So if u guys have any fixes to this issue or other suggestions of what I need to try that would be massively appreciated as I've exhausted all my options.

Thanks!