What’s this ?
No file inside the directory, but I can read this : {"status":"error","message":"Unauthenticated","code":403,"exception":"Kirby\\Exception\\PermissionException","key":"error.permission","file":"authentication.php","line":10,"details":[],"route":"(.*)\/lock"}
If uploading files or creating and deleting pages works, but saving edits doesn’t, then it’s definitely a problem with PATCH requests.
And you will have to find out if you can somehow enable them, e.g. via the .htaccess or if your provider is willing to do it. If not, then you will have to change providers, because PATCH requests are required for the Panel/the REST API to work.