Hi @rmr.nl, welcome to our forum! Are you using http://veilig.kpn.com/?
It could have been a temporary issue, could you try again?
If that does not work, could you try a different browser or a different device?

I tried again and It does not work.

yes, I used the mentioned link: veilig.kpn.com

trying with a different browser:

Same result.

Using a different device… same problem.

That's quite peculiar!
Could you also try with your plugins disabled and/or with a private browsing window?
The issue seems to be you're able to load our website but not getting the F-secure bit (KPN veilig)

I just tried this with my own account and everything seems to be working fine here so I'm not excactly sure where the problem lies.
If the above steps don't solve this issue, could you unlink your products in your MijnKPN, re-link them and try again?