Lol I was. Reading down thinking somewhere hikmission is going to be mentioned
But yes cleaning needs consideration, although the most residential either don't clean at all , or use an abrasive cloth on the ceramic and wonder why it's fogged up at night , muppets
Have you measured the battery voltage with good meter , not Chinese stuff that will give you wrong readings
For the sake of £4 change battery see what happens
Sounds to me it's been shut off because of faults , and even factory defaulting won't help you, even though that info isn't not given out on this site
If it was working most systems just sit there happily in standby and if shut down because whatever fault occurred they didn't want the expense to fix it
If you know what your doing just sawp it live
Otherwise disconnect all four from panel , it's easy to take off 12v at PC end and still make a mistake
You have fire extinguisher nearby?