So I have created a pack (slowly getting popular) and today I released an update after fixing a big tree mod issue (it downloads as a .jar.zip file) which was what I had included in the previous update but in this new version I removed that and installed the correct .jar file but whenever I try and click update it says "update failed: a file is locked by another process. Cannot update this profile."
Further information: When I check pack options I have allowed the pack to be unlocked.
Extra Information: When I try deleting the pack it says: "Cannot delete profile. File or directory is in use."
I don't want to be that guy but have you tried rebooting your computer? If you've got a file locked in any program, that generally means the process/file is in use somewhere. Be that a borked Java process or anything else.
You can click on the pack and then the gear. Select Open Folder and it will open file explorer/ my computer and you will be in the modpack folder itself. Click on the directory before labeled Instance and it will show all the modpacks you have downloaded. Right click the folder and click delete and it will put it in the recycling bin. I tried deleting the pack after and it worked. Maybe that will help.