it was fine for the first 2 weeks after i got it with my ryzen 5 1600 and was able to hit up to 2400 rpm when i set it to full speed. but about a week ago it max's out at 800 rpm and refuse's to go past it no matter what i do
Try connecting the Spire fan power cable to one of the motherboard's case fan ports (3 pins) or directly to the PSU.
This is just to see if it ramps up to full speed when not under control by PWM connection (4 pins).
If it goes to full speed under a 3 pin fan connection then you need to look in BIOS settings for CPU Fan settings and also use AMD Wattman to configure the CPU fan to be more aggressive.
If the Spire Fan doesn't go to full speed while connected to a 3 pin connection and still stays at 800 RPM than you need to open a online AMD Warranty Request to see if AMD will replace it under its 3 year Warranty that comes with the processor if you purchased the processor separately as a bundle at a Retailer or Vendor.
Could be a defective sensor on the Motherboard or the software you are using to monitor the fan's RPM is not working correctly.
What does AMD Wattman or BIOS indicates the speed of the fan?