Can't import MTGO dek files to my collection?

{"ops":[{"insert":"It's a fresh export from MTGO in xml format, 1,64MB in size, contains about 18000 cards.\nAfter i select the file to upload, nothing happens. \nI tried all the possible options, also cleared my MTGO collection beforehand.\nOther sites like cardhorder can process the exact same file without any problem.\nI know that this worked some time ago.\n\n"}]}