Connection issues

I can connect to some websites from my PC (connected to the gateway by ethernet) but frequently get "your connection is not private" or the xfinity captive portal page.  My mobile phone frequently says it is connected to wifi without internet.  And I have been having trouble connecting remotely to work while at the same time I can still browse certain websites.

I texted the on it team and got a call and was told they are doing maintenance in my area.  But wouldn't an interruption due to maintenance mean a complete disconnect?  Are these issues possibly related to maintenance?

The frustrating thing is that I can't designate a different phone number for them to call since I have to text from my cell phone.  I get my cell service through a cellspot connected to the internet.  So inevitably they send a reset signal, sometimes without warning, that cuts off the call.  And they can't call me back because they are just routed the next call.

Thanks.