Hello @Thaddeuskrm 

Maybe this link will help you.

https://www.ssl2buy.com/wiki/how-to-fix-err-ssl-protocol-error

I tried everything from this side and nothing. There is the same problem on the phone as on the laptop. But connecting on the phone via wifi to another network, the site works without any problems. I will add that I use the phone as a router. Andinformation about the expiration of certificates appears

@Thaddeuskrm

On T-Mobile 4G I can acces the website so it's not a network related problem.

Try resetting the network settings of your phone once.

Resetting the phone's network settings did not help.  After another attempt, a message appeared. 

@Thaddeuskrm 

You can click on ik begrijp het, maar wil toch verder.

Extra veilig online is causing this that you cannot acces the website, a moderator can stop Extra Veilig online or if you have unlimited Plus than you can turn it off in the app > meer > blokkades.

@Waqqas 

The website opens.  Thank you very much for your help :)

@Thaddeuskrm

Do you have a unlimited Plus subscription or not? Extra veilig online is €1,49 each month with other subscriptions .

If you don't need it let ít be stopped by a moderator

@Waqqas 

Yes, I have unlimited Plus.

@Thaddeuskrm 

If you look in the app > meer > blokkades, you can block this service there.