Exported FLAC files not readable by Archive.org

Windows 10
Audacity 2.2.0
Exported files as FLAC at highest quality setting; attempted to upload FLAC files to Archive.org’s Live Music Archive but received I/O error. Tested FLAC files locally and was able to play back on Winamp with no problems. This was my first attempt using 2.2.0. Have not had this problem with earlier versions.

That sounds like a problem with Archive.org.

Exported files as FLAC at highest quality setting;

FLAC is lossless, so there are no “quality settings”. There’s a compression setting that takes a bit more time and gives you a bit more compression (or vice-versa)

And, you can change the bit-depth and sample rate that you feed-into FLAC. If you used something like 24-bit/192KHz, maybe Archive.org can’t handle that.

Version 2.2.0 does have a “highest quality” vs “fastest” selection for FLAC files. I didn’t notice it at first but when you export the file there’s a slider in the dialogue box. In any event, the recording was made in 24bit/96kHz which Archive has never had a problem with before. I also didn’t mention earlier that after entering metadata, the status dialogue box, which shows the progress of the export, is disabled

Please post a screenshot so that we can see what you are referring to.