Some Squarespace IPs are blocked by firewalls. What can I do?

Hello dear forum,

For some time now I have had the problem that Squarespace IPs appear on blacklists. See screenshot. The result is that firewalls classify the sites as unsafe and block them. 
Two of my customers have had this problem and we have had it ourselves within the last two/three weeks. This reflects badly on my agency and is of course a bad situation.
What can I do? Or can anyone tell me whether Squarespace can get to grips with this problem?

DNS Checker:
https://www.nslookup.io/domains/www.superidee.de/dns-records/
Blacklist Checker:
https://www.virustotal.com/gui/ip-address/198.185.159.145

I look forward to your answers.
Ulf

Translated with DeepL.com (free version)

This issue does not originate with Squarespace, when it happens it is caused by the visitor's internet provider or the viewer's firewall. That is why it happens randomly. I don't get blocked using Xfinity/Comcast when visiting a Squarespace site, but I know some other internet providers have previously blocked Squarespace. 

Your customer SSL certificate is showing no errors:

https://www.sslshopper.com/ssl-checker.html#hostname=https://www.superidee.de/

Contacting the Internet Provider's customer service is the first step to fixing this.