Server not available Android 3.18.0

In the Nextcloud app, the server is not available when updating. You can access the server in the browser. Nextcloud Android app version is 3.18.0. Devices with app version 3.17.0 can access the server. There are no problems with Iphone models.
Does anyone have any idea what I can change?
App has already been reinstalled.
Thank you so much for your help.