Right now, the only way I can see to do this is to delete the account and re-create it. This is a horrible usability problem.
Thanks for your report, but this is a duplicate of #219.
Duplicate of https://forums.bitfire.at/topic/2121/please-support-nextclouds-singlesignon-sso
The problem comes from Deck. Please follow up here: https://forums.bitfire.at/topic/2427/404-when-uploading-a-locally-modified-resource
For now, we will use 90 days as default value.