Payolution IPNs beeing blocked

As of today suddenly the IPNs from Payolution won’t come through to our website. Configuration of those services did not change in the last months, so I am wondering what happened on the weekend. Strangely the IPNs from Paypal work just fine.
Setting firewall to essentially off or, and disabling WAF does’nt help. Purging cache or developer’s mode won’t help either.
Disabling routing DNS traffic through Cloudflare seems to help, but that is obviously not a solution. So I’m a bit stuck here.
I am thankful for any hint…

How about allowlisting them? I don’t see any IP address listings at Payolution, but here are the Cloudflare instructions on how to add them if you find out what they are:

… yes, that was my closest guess to the problem, too. all that sounds like an firewall issue. the payolution IPs are already whitelisted, but have to dig into that more I guess.

… so despite my best guess, something going with the firewall, after updating the whitelist nothing happened. Same behavior of IPNs don’t coming through.
As I learned in the last couple of months to be more patient with Cloudflare, the problem fixed itself today. After 2 days of grey clouding Cloudflare and switching it on again today, now things are back to as they were.
Without any change of settings to the services involved it is working again.

So, I’m happy on the one side, but I’d really liked to know what the problem was in the first place.