No connection time-out on a mac

I’m pretty new to this forum, so I hope someone can help me
I work on a iMac 13.6 and my nextcloud is hosted by owncloud. Due to some problems at owncloud they provided me with a complete new installation and new password. I used that one in the nextcloud app (3.10.0git (build 17671) but I forgot to adjust it in cloudmounter. So the last one kept searching and at the end the site was blocked on my iMac. On my iPad I can still enter it.
So I hope someone can help me how to fix it (I don’t have a windows computer…)
The helpdesk advised me to use bruteforcer but that is not for a Mac.