I have had a 4g extender (SLS-BU103) for 3 years with no issues. In the past few weeks, phones are not connecting to it. My apartment has very poor - but not zero - signal, and phones used to choose the extender over the poor signal.
I have an iPhone XR from work and a Pixel 4a on Xfinity Mobile (a Verizon MVNO), and neither will connect. I'm am occasionally able to get the 4a to connect by toggling airplane mode, but that's rare.
If I log into the configuration page on the extender, it says the status is In-Service, but there are no connected devices.