Help!!! Skimmer not skimming

[MGAMAL]

My skimmer (octo regal 150S) suddenly stopped skimming and lots of micro air bubbles appeared every where in the tank and sump, I was patient for around 3 weeks by doing all the required skimmer adjustments with no progress, so I decided to replace it by deltec 1000i and after around 10 days it started skimming for around 4 hours and then stopped so I send back to the shop and he kept it running for one day and was perfectly working there. Once I took it back to my sump it didn’t work. I stopped dosing NOPOX and after one day it skimmed for 5 or 6 hours and till date for more than a month it is not skimming.
please help

 

[lapin]

First question
Does it make bubbles?
Second question
How clean is your tank?

 

[Omarons]

Watch bulk reef supplies youtube video around skimmer adjustment
The best way to tune your Protein Skimmer: Learn how in just 5-minutes!

 

[jda]

If this is a new(er) tank, then it won't be skimming anything yet.

 

[Reef man 89]

Tank need waste in order to produce skim mate if there is nothing in the tank for the skimmer to take out the bubbles will just collapse and won’t create a foam head

 

[MGAMAL]

The tank is one year old and the reef octopus wa working fine till it suddenly stopped 2 months ago and I tbought its a skimmer or pump issue so I replaced it by the Deltec and its now running for more than a month.
I watched BRS video and tried to adjust the air but all what I got is bubbles with no foam, no dirt comming in the cup