Netgear Switch GS324TP PoE not working

For several days I have been in trouble with my GS324TP (5,5 year old). I first noticed that Alexa (located in 2nd floor) stopped connecting to my wifi (we have a Fritzbox 7590 in the cellar) and a Ubiquiti Unifi AP AC Pro/Lite on each floor. Wifi (switch + access point) connection was frequently interrupted. I updated the switch's firmware from .38 to .44, made several resets... Nothing helps, the wifi - as well as the LAN connection - remained unstable and at the moment isn't working at all. At the switch der are only shining the upper leds, not one led in the poe row. Is it possible that the switch is over or has mainly problems with poe?

I tried to connect my old notebook (which can be connected to lan cable) with a lan socket, the notebook reclaimed "no connection to internet".. 

Sorry for my english - haven't been using it for several years now... Any ideas how to fix this problem?