I too was infected by Grancrab 5.1
The extension of the files is JYUTFTSIJQ and the txt name is JYUTFTSIJQ-DECRYPT
Please advise. Thanks
Every version of GandCrab from 5.0.4 onward is NOT decryptable.
Save your files to a USB or a disk drive (or even cloud storage) and wait for a possible decryption tool. Some ransomware variants might take years to decrypt or there is no chance for decryption. So, if you didn't have a backup of those files you cannot recover them at the time being. Try a data recovery software, but I doubt that will work. Renaming mp3 files back to their extension might work.