HP T120 OOP sensor replaced (genuine part), still have "Paper from roll cannot be detected..."

[jimsmith5358]

Hi everyone, thank you for reading my post. I'm beaten, and I'm hoping someone can help. 
I have an HP DesignJet T120 A1 (24") plotter/injket with an A4 and A3 feeder. The firmware is upto date with the latest version, as are the drivers and software - I've tried it on about 5 different computers, all running (legal!) and upto date Windows 10 Pro (1809 build) or higher, and one running 10 home (all x64) 
I have tired connecting via Ethernet and via WiFI, and can connect to the printer, no problems. It fires up ok, and states that I'm running low on Cyan (true, but not going to replace if I can't fix it!). 
I can print onto A3 and A4, but when I try and use the roll (HP Printing paper!) it tells me that it cannot detect the paper, and that I need to load a roll. I went though all the trouble shooting steps and it was all going well until it told me there was a problem with the Out Of Paper Sensor (OOPs (!)). I ordered a part from a LEGIT company, HP boxed branded (and priced!), which came with a new ribbon (FFC) and I carefully removed the old one, including the cable, and replaced it (paying attention to which way round the cables were etc taking photo's as I went, and colour coding and numbering everything. I put everything back on, put the housing back on the end but only put one out of five screws in (just in case...) to test it....and got the exact same error! Yes, I rebooted, unplugged, pushed gently but firmly on the power button for 60 seconds to make sure it was fully drained of power, then fired it up again, giving it time to be detected by the computer(s) which it was and to 'warm up'. I then ran the diagnostics again, and same answer. I 100% ordered the correct replacement part, per the serial number of the machine and the part number. I even removed the red sellotape that comes with the new on to hold the OOP sensor 'flag' down - same error message. Tempted to give it a tap or ten with a 5lb 'adjusting tool', but thought I would ask you good people first. It's about 5 years old, and 'broke down' about a year ago, I've just not gotten round to fixing it as I wasn't doing a lot of CAD work, which I'm starting to now, and don't want to bust out £1,000 for a new model - unless I absolutely have to! 
Again, thank you for taking the time, and I hope someone has an idea or two! 

[Valsimot]

Download yourself service manual and run  OOPS test from test menu to see will it pass.

The OOPS is used both for roll and sheet, so if your printer was loading sheet before replacing OOPS it's very likely that your old OOPS is working just fine.

[jimsmith5358]

My apologies - I should have said, I have the technicians manual and have followed the 'ITIT', but it just says 'contact engineer'. I just wondered if anyone else had had the same issue and got round it without calling in an engineer. 

Many thanks, Valsimot for taking the time to read and answer my question.

Jim

[Valsimot]

When you are loading roll does it starts to feed roll automatically inside the printer and after the printer is over with checking you get an error message?

Can you get an A1 sheet and try to load or A3 roll and try to load?

I am suspecting when carriage assy with a line sensor (a light sensor that reads the paper) goes far to the left side ( watching from the front) to check for paper width and skew something goes wrong. If my suspicions are on the right track then you will not be able to load A1 sheet but will be able to load A3 roll. 

[jimsmith5358]

Fantastic! I'll try this as soon  as I get home. It's these sort of ideas I'm looking for - practical ones from people who know these things inside out. I can GENTLY force the paper in by hand as much as possible (like I've done on any other plotter) then it takes over and pulls it in - or it used to. I was hoping there would be some sort of flag or sensor to pick up the A1 roll that might be stuck or need replacing. I'll check this later and let you know... THANK YOU!