I’m having the same issue. With a particular set of folders too. My vault is fairly large, in the 250gb range - and it works perfectly on PC but I keep running into this error on iPad. It also is very consistent. I.E it affects the same folders once it starts. Health check fails to fix issue.
I have found a workaround to make it work and am posting a log here to help the team achieve a long term resolution. Inside of the logs I could find the folder it was trying and failing to access. I then navigated to the encrypted folder manually and forced iCloud to download all files inside. Once done - it could open it perfectly in Cryptomator.
Why it failed to call the file download on its own - and why it only happens with certain folders is a mystery. I hope this log helps. It says something about avoiding a resource deadlock. Anyway thought it was interesting. I’ve also obfuscated part of the unencrypted path name for privacy, but the log should still be sufficient enough to identify error. This has been an ongoing problem for some time so I’m happy to learn I have a workaround - dispite it being a pain to do.
2023/11/23 06:09:54:257 acquired lock for path: CloudPath(path: "/T*****ts/U******d/New 9-2023") - type: read
2023/11/23 06:09:54:258 LocalFileSystemProvider: fillCache(for: /d/T7/4TI4OZW57PKEQCD4M4G6SNQ4SADLLV) called with startAccessingSecurityScopedResource: false
2023/11/23 06:09:54:264 LocalFileSystemProvider: fillCache(for: /d/T7/4TI4OZW57PKEQCD4M4G6SNQ4SADLLV) failed readingIntent evaluation with error: Error Domain=NSCocoaErrorDomain Code=256 "The file “4TI4OZW57PKEQCD4M4G6SNQ4SADLLV” couldn’t be opened." UserInfo=\{NSURL=file:///var/mobile/Library/Mobile%20Documents/com\~apple\~CloudDocs/Sensitive/Tps1/d/T7/4TI4OZW57PKEQCD4M4G6SNQ4SADLLV, NSFilePath=/var/mobile/Library/Mobile Documents/com\~apple\~CloudDocs/Sensitive/Tps1/d/T7/4TI4OZW57PKEQCD4M4G6SNQ4SADLLV, NSUnderlyingError=0x11a91aa50 \{Error Domain=NSPOSIXErrorDomain Code=11 "Resource deadlock avoided"}}
2023/11/23 06:09:54:266 enumerateItems failed with: Error Domain=NSCocoaErrorDomain Code=256 "The file “4TI4OZW57PKEQCD4M4G6SNQ4SADLLV” couldn’t be opened." UserInfo=\{NSURL=file:///var/mobile/Library/Mobile%20Documents/com\~apple\~CloudDocs/Sensitive/Tps1/d/T7/4TI4OZW57PKEQCD4M4G6SNQ4SADLLV, NSFilePath=/var/mobile/Library/Mobile Documents/com\~apple\~CloudDocs/Sensitive/Tps1/d/T7/4TI4OZW57PKEQCD4M4G6SNQ4SADLLV, NSUnderlyingError=0x11a91aa50 \{Error Domain=NSPOSIXErrorDomain Code=11 "Resource deadlock avoided"}} for identifier: NSFileProviderItemIdentifier(\_rawValue: DA0D5AD9-B563-4858-9B72-660272600DA5:66)
2023/11/23 06:09:54:280 FPExt: urlForItem(withPersistentIdentifier: NSFileProviderItemIdentifier(\_rawValue: DA0D5AD9-B563-4858-9B72-660272600DA5:66)) called
2023/11/23 06:09:54:280 FPExt: item(for: NSFileProviderItemIdentifier(\_rawValue: DA0D5AD9-B563-4858-9B72-660272600DA5:66)) called
2023/11/23 06:09:55:740 FPExt: enumerator(for: NSFileProviderItemIdentifier(\_rawValue: DA0D5AD9-B563-4858-9B72-660272600DA5:66)) called
2023/11/23 06:09:55:741 FPExt: item(for: NSFileProviderItemIdentifier(\_rawValue: DA0D5AD9-B563-4858-9B72-660272600DA5:66)) called
2023/11/23 06:09:55:756 currentSyncAnchor for DA0D5AD9-B563-4858-9B72-660272600DA5:66 called -> return: Optional(CryptomatorFileProvider.SyncAnchor(invalidated: false, date: 2023-11-23 06:03:12 +0000))