Zoho Connection problem in public areas

Zoho Connection problem in public areas

I would like to ask you a general question regarding the access of Zoho in public places like restaurants, coffee shops etc.

Me and my colleagues when we work in this kind of public places (with our laptops) in most cases we cannot open the Zoho Platform (Mail, CRM etc.).
It returns 'This site is not reachable'. But when we are connected with our mobile data then we can open the sites.

Quite strange? I think it is not a wifi problem in these shops. Is it because of 'https'?

Does anybody here have the same issues with me and what we can do in this case in order to be sure that whenever we are, we will not lose the Zoho access?