I have two access points EAP225 (hardware versoin 3.0) in my network that have been working fine for years.

I have now purchased an extra EAP225 (version 5.0) and connected it with the same network settings. But now I no longer have contact with an Apple Airport Express that connects to this new access point!

When the Airport is connected to one of the older access points, it appears neatly in the network (also with Apple's Airport configuration), but as soon as it connects to the new version, the Airport disappears from the network again.

Anyone have an idea how this is possible? Could it be due to the hardware version?