I've been using 9020 Powerline adapters for some years. One is in a studio at the bottom of the garden; last week I experienced trouble streaming live Bridge on RealBridge (graphic interface with live audio and video). Speed tests showed 0.5 Mbps, and the Status on all three adapters showed red. I reset them all. Status showed green briefly but reverted to red.
Do these devices wear out?
I've switched to Wifi, using a new USB 3 aerial. The SmartHub 2 sends a strong enough signal about 35 metres through 2 panes of glass, pretty well in direct line of sight, to provide about 40Mbps download and 30Mbps upload. Although I can't understand why an iPad in the same location achieves 128Mbps; maybe the signal to the Windows 11 desktop degrades over the USB 1 metre cable.
All electronic components have a finite lifetime and it follows that any electronic device also has a finite life, if (as you say) you've been using them for some years and a factory reset hasn't resolved the problem then it could be that one or more of the devices are faulty.
Highly unlikely that all three would have failed at the same time. To test, label them 1, 2 & 3 & connect 1 & 2 in a double socket near the router & connect to a laptop. If no good replace 2 with 3. If that works you know 3 is suspect. If not, replace 1 with 2 & you should have a good pair for future use. If all combinations work then maybe you have an issue with the mains wiring to the studio that warrants further investigation.
As for the WiFi speed difference, which USB adapter did you buy? Maybe it isn't 5GHz capable or just doesn't want to connect to 5GHz at that distance. That's the problem with having the two WiFi channels bonded, you have little control over which one you connect to. If the adapter is 5GHz capable then try "forgetting" the current connection on the PC, turn off 2.4GHz temporarily on the router & see if the adapter will connect at the higher speed.
Generally 5GHz gives faster speed over short distance & 2.4GHz provides better (but slower) coverage over greater distance.
Thank you, Les and rbz,
I'll have a go at your suggestion, rbz, but don't hold much hope, because the "A" adapter is showing Status red, and it's just a short ethernet cable length from the Hub. I'd already tried switching the original "A" then resetting them all. I've removed the one in the studio as the aerial (PiAEK USB Wifi Adapter, Dual Band Wifi Dongle 2.4GHz/300Mbps 5.8GHz/867Mbps USB 3.0 Cradle and Extension Cable) is performing well (170/46 just now).