Is there a limit to how large a file can be and lightroom Classic CC still be able to create a 1:1 preview? I have a Tiff that is 26246 x 2899 pixels. When I try to view it at 1:1 or any other size except "Fit" in the Library module, it refuses to draw. I can view it in any size in the Develop module or Photoshop, but not the Library module. Does the Library module have a size limit, and if so, what is it?
The limit is 65,000 pixels maximum on either side or 512 Megapixels.
A 26246x2899 (76 Megapixels) TIFF file is well within those limits. I can confirm what you are seeing using a 16 bit TIFF with those dimensions inside LR Classic 2018 on Windows 7 and 12GB of memory. It just shows the gray background with no preview image with 6GB of free memory available.
I suggest posting this at the Photoshop Family Forum as a 'Problem.' Provide full details as above and place a link to the report here so others can add their 'Me To' vote. This is the best way to get Adobe's attention and the issue fixed.