I got about a dozen messages today which, upon revise listing upload, all say “This auction listing type is not valid. Please see the API documentation for valid types.”
So far, these were all changed from FIXED PRICE/BIN to AUCTION.
Only changes were the TYPE OF SALE, PRICE, and DURATION (from GTC to 7 days".
As an experiment, I tried just revising PRICE and DURATION and that too yields an error message, though this is a different one:
"The duration “7” day(s) is not available for this listing type, or invalid for category “801”.