Photos exported from Lightroom are limited to 2593x1729. Quality is set to 100, resize is unchecked, and none of the options on the left panel are checked. I have a photoshow coming up very soon and I'm low key panicking!

Assuming that your original is a raw file, then there is a better option that you could try first if this happens again. Checking → resize to fit → long edge → 5,400 means that Lightroom will use simple interpolation to increase the size of the cropped output. Lightroom can also increase the size of the original to 10,000x8,000 via AI Super Resolution (if you did not already use Denoise). That is a much more advanced way of interpolation, that would have made your cropped output 5186x3458 pixels.

Okay, apparently I can’t delete my own posts. I fully intended to remove this since I seem to have fixed the issue.

I needed to check → resize to fit → long edge → 5,400.

The image in question is very cropped in and I didn’t understand why the photolabs website was warning me about low resolution when the image (despite being very cropped) had heaps of detail. Like, you could not tell it was cropped. Anyway, please delete this post.