Failed to connect to sentry.io port 443: Connection refused

We are trying to use sentry.io on a shared hosting environment from world4you. Sentry is integrated as a Symfony Bundle within a Contao 4 installation.

Unfortunately, no exceptions are sent to sentry. I noticed, that the hosting environment is unable to connect to sentry:

$ curl https://sentry.io/                                         
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current                 
                                 Dload  Upload   Total   Spent    Left  Speed                   
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (7) Failed to connect to sentry.io port 443: Connection refused

According to the hosting provider, no outgoing connections are blocked and it seems that sentry is simply refusing the connection.

Does sentry refuse the connection when coming from specific servers? How could I resolve this issue?

So far I have also noticed this on my end when I simply want to access https://sentry.io/ via my Smartphone’s browser - depending on the network from which I am connecting to. It seems the Sentry servers are really blocking connections from certain IP ranges.