Plusnet pop-up login screen

[#1]

I've been using Plusnet for over two years without any problems until last Saturday. Suddenly, all the devices in my family — including our Mac and Windows laptops as well as our iPhones — started showing a Plusnet pop‑up window from time to time, as shown in the attached screenshots. I tried logging in at first, but it only gave me the “We’ll be right back” error message. I later realised that I can still access the internet by simply closing the pop‑up, but it’s quite annoying because it keeps appearing repeatedly.

Could anyone advise us on what we should do to resolve this issue? Many thanks.

[#2]

@bearhung Three different screens, all with different possible meanings/reasons. Out of interest, your payments are up to date, aren't they?

[#3]

I am crystal ball gazing ...

Recently a poster has unexpected Plusnet Pop-Ups appearing on their kit and it turned out to be a problem with the payment method having expired or failed.  Might be worth a check in the Plusnet Members Centre.

[#4]

@PhilipHeyes That was what I was suggesting was checked, but I suppose your answer was rather more direct.