I ran into some trouble while Updating to NC 13.0.4 regarding encryption. As long as Encryption was installed and enabled no login was possible – WebDAV and Clients received HTTP/503, WebUI didn’t show the login form but only „Bad Signature“. Also occ failed with the same error – „bad signature“. The previously working version was afair 13.0.1, since downgrading isn’t supported I can’t say much for .2 and .3. Inside the log (see below) I could see the error being caused by the encryption module. There might be the odd encrypted folder still present in old accounts, but since it never worked for me reliably it’s disabled for everything currently in use. External solutions are IMO the way to go.

{"reqId":"xyz","level":4,"time":"2018-07-20T17:53:17+00:00","remoteAddr":"xyz","user":"--","app":"webdav","method":"PROPFIND","url":"\/remote.php\/dav\/files\/xyz\/","message":"Exception: {\"Exception\":\"Sabre\\\\DAV\\\\Exception\\\\ServiceUnavailable\",\"Message\":\"OCP\\\\Encryption\\\\Exceptions\\\\GenericEncryptionException: Bad Signature\",\"Code\":0,\"Trace\":\"#0 [internal function]: {closure}(*** sensitive parameters replaced ***)\\n#1 \\\/var\\\/www\\\/html\\\/3rdparty\\\/sabre\\\/event\\\/lib\\\/EventEmitterTrait.php(105): call_user_func_array(Object(Closure), Array)\\n#2 \\\/var\\\/www\\\/html\\\/3rdparty\\\/sabre\\\/dav\\\/lib\\\/DAV\\\/Server.php(466): Sabre\\\\Event\\\\EventEmitter->emit('beforeMethod', Array)\\n#3 \\\/var\\\/www\\\/html\\\/3rdparty\\\/sabre\\\/dav\\\/lib\\\/DAV\\\/Server.php(254): Sabre\\\\DAV\\\\Server->invokeMethod(Object(Sabre\\\\HTTP\\\\Request), Object(Sabre\\\\HTTP\\\\Response))\\n#4 \\\/var\\\/www\\\/html\\\/remote.php(72): Sabre\\\\DAV\\\\Server->exec()\\n#5 \\\/var\\\/www\\\/html\\\/remote.php(167): handleException(Object(OCP\\\\Encryption\\\\Exceptions\\\\GenericEncryptionException))\\n#6 {main}\",\"File\":\"\\\/var\\\/www\\\/html\\\/remote.php\",\"Line\":70}","userAgent":"Mozilla\/5.0 (Windows) mirall\/2.3.2 (build 1) (Nextcloud)","version":"13.0.4.0"}

The usual literature suggests to disable the encryption module using occ – not quite helpful in my case. Deleting the encryption app on FS-level did revive occ and Web but the App now failed due to missing encryption. My solution was to disable encryption using SQL instead of just deleting it:

UPDATE `oc_appconfig`
SET `configvalue` = 'no'
WHERE `oc_appconfig`.`appid` = 'core'
AND `oc_appconfig`.`configkey` = 'encryption_enabled';