Battery not detected and no fans

So I bought the ifixit battery replacement for my MacBook Pro about 2 months ago and the replacement went well. All working, battery functioning as expected.

Then yesterday, I wake up to what seemed like a dead MacBook Pro, I assumed it must be that I had left it unplugged and the battery had drained overnight, but there was no battery dead message when holding the power button which I thought was odd. Then I plugged it in to MagSafe and it powered up. Then after half an hour I disconnected it, and the screen went black immediately.

I’ve reset SMC two times and run diagnostics which gave the error PPT001 (battery not detected). In addition, I’ve noticed that the fans never boot up at all and the CPU seems throttled as it’s acting very sluggish.

I’m not sure whether this is a problem with the battery I replaced or if just by coincidence the SMC has given up. I’m planning on getting a new MBP when they release them hopefully next month, but I need this one to hang on just a bit longer.

Any insight/suggestions welcome, thank you!