Experiabox v10 port forwarding not working

Hey boviorco, welcome to the forum! Looking at your screenshots, I think you need to make separate forwards for TCP and UDP. If I remember correctly, the combined version doesn't always work well.

Perhaps @wjb can take a look to confirm or deny my suspicion and further assist you

The reason why you don't see the ports as "open" is due to the fact that there are no services listening to the ports you forwarded that would answer the message from such portchecker sites.
Normally UDP is used for Wake On LAN and UDP can't be checked at all through such sites.
Please note that you should only forward UDP port 7 or 9 (9 = standard) for WoL.
I only forward UDP port 9 to my Synology NAS running the Wake On LAN Gateway that I developed for the Synology NAS.

Application:

Port-forwarding to the IP address of my Synology NAS:

Please note that in "real life" I use a different port on the Internet like for example port 56509 meaning that the start- and end port are set to 56509 where the start- and end mapping port remain on 9.

PS. Do you have a Synology NAS and did you download the Wake On LAN Gateway last Monday around 19:00h?

Please note that the IP address of the workstation will be "forgotten" by the Experia Box a short while after the workstation has been switched off. The port forwarding will than not work anymore meaning the WoL magic packet will not reach your workstation anymore.
If you face this issue, you will need to have a server that implements "subnet directed broadcasts".

Yes, unfortunately that is also going to happen when a DHCP binding has been defined for the machine. The IP address will not change as long as a DHCP binding has been defined for the machine or the machine reconnects within the remaining DHCP lease period. (Normally 24 hours.) The IP address is however removed from the ARP list within a few minutes. The exact time depends on the router, but it will not be a long time after which the IP address will be "forgotten".

I'm a bit confused since as I mentioned before the IP address hasn't changed and the last time the machine was switched on was more than a month ago.
All this period it's been off, therefore the reconnection has happened after quite some time..
How can I check this lease period or otherwise set it to a fixed IP?When you have defined a DHCP binding for the machine, it means the DHCP lease time is infinite and therefore the machine will always reconnect within the remaining DHCP lease time. This is why the IP address does not change.

Would it be sufficient to assign a fixed IP address to the machine?No, unfortunately not. The ARP table is the table that contains the actual overview of connected devices providing the routing information where to find which device. This has nothing to do with the DHCP settings. By design devices that are disconnected from the network for a few minutes will be removed from the ARP table.
There is nothing you can do about that other than ensuring the network adapter remains active, even when the machine has been turned off. I doubt if this is supported by the network adapter in your workstation and if this is a Windows machine I am even convinced this will not be supported.