Waters Alliance 2695 no pressure and no pumping Help???

[MSavet]

Hey Everyone,
So we have a waters alliance 2695 HPLC which had PM done a month ago, the instrument was running fine for a couple of days and then lost all pressure and flow through the inlet of mobile phase. I was running a Mobile phase of 0.1% monobasic potassium phosphate in methanol, I immediately went and sonicated the mobile phase assuming it just needed degassing and ran pure IPA through the system to clear any bubbles or salts caught in the line... Nothing no flow or pressure increase.

After research I went and sonicated the check valve cartridges in water for 15 then methanol for 15 and nothing still, I did wet prime, then Dry prime (nothing came from the lines), I tried making the flow lower and ran it at .2mL/min overnight, and it lost prime.

I am at a loss for what it could be, i checked the inline filter and it was clean nothing wrong with it.

Any help would be greatly appreciated!!

[Hollow]

are all lines affected or only the one with the buffer?

My thinking goes to a clogged GPV (gradient proportioning valve)
What if you remove the line from the GPV to the primary pump, then open line by line with the dry prime?
Is solvent flowing from the center line? For all lines?
If that seems ok, the transfer line may be clogged.
If no flow for any channel -> gpv seems clogged.

maybe you can try to "reanimate" the clogged part by flushing with warm water.

IPA and phosphate buffer wasn't a good idea any way.
Always use water as an intermediate step when using phosphate buffer.
And if made out of salts, we do membrane filter prior to use.