If the CR2 files have the expected file size but most contain no usable embedded JPEG preview and multiple recovery/repair tools can’t read them, there may be significant corruption in the RAW structure itself. At that point, general recovery software is often no longer enough.

A sensible next step is to try a specialist who understands Canon RAW internals. One community recommendation is Dave Coffin, author of dcraw, who has experience with Canon RAW formats and offers consulting/data-recovery-related services. If anyone can assess whether the files are repairable, a low-level RAW-format expert is more likely to succeed than consumer recovery tools.

Important: stop writing to the original card or original storage immediately, and keep untouched copies of the damaged files before attempting anything else. If the embedded preview is also missing or black, that usually means there may be little intact image data to salvage, so professional help may be your best remaining option.