I attached a new HDD to my Ubuntu Server and mounted it as /mnt/NextCloud-AUX-Storage I then logged on to my Nextcloud and attached it but I get an error when I try to upload anything

[TaylorSwifies]

Hey guys! So, I’m using the latest version of Nextcloud from the Snap store and its amazing I have one small problem I have a feeling it has to do with permissions but I cant put my finger on it.

Version and OS info:
Latest version of Ubuntu Server 20.04.3 LTS

I attached a new HDD to my Ubuntu Server and mounted it as /mnt/NextCloud-AUX-Storage
I then logged on to my Nextcloud and attached it, it shows up but I get an error when I try to upload something. I’ll provide screenshots with the permissions and so on. Any suggestions?

[TaylorSwifies]

more screenshots:

[Mornsgrans]

Please find the default data storage folder of Nextcloud and look at its permissions (owner, group) - mostly www-data:www-data. The new additional storage will need the same settings, if I am right.