Nextcloud - Collabora Online Conecting Issues

Hi,

I setup collabora online on my ubuntu server and its been working like a charm, but i discovered an issue a few days ago that at first i though ok its a conection issue on the client side, but now i realized its something else.

The issue is that most of my users r on the same ISP as me and as my server is, but some belong to a diferent ISP, its the 2nd biggest ISP in my country, everyone that its on the same ISP as me can work documents on nextcloud just fine without an issue, but the ones on the other ISP cant load documents at all, it just stays there on the loading screen and then shows an error saying something like they dont have permisions to access the file and that they should contact the administrator.

I have no restriction whatsoever on whom can access the platform, if they r an user on the platform they should be able to work any documents they want freely, but sadly this is not the case and only happens with the users on that ISP, so i was wondering if someone can help me figure this out and fix it once and for all