My POL friend Robert Jones recently gave us some useful advice on how to treat a canvas which rejects paint. He has granted me permission to copy you in.
Here is what Robert said. Very often, unfortunately, canvases and boards are treated with a fungicide, especially if they’re made abroad and shipped over here. You can see this if you hold the board/canvas up to a raking light – it shows as shiny, glistening areas in the weave. This is easier to deal with on boards, which are more robust, than on canvas, but the short answer is to wash the cloth with lukewarm or cold water; use a nail brush, even a little plain soap if necessary to get this stuff off. Towel dry it if possible – just pat it, and if shiny spots still remain, have another crack at them.
Acrylic paint won’t adhere to the fungicidal preparation; or even worse, it will until the point at which you come to varnish it, when it may lift and ruin your work.
Once you are satisfied that all of this wretched stuff is out of your canvas, I would indeed paint it with two coats of acrylic gesso – I use the Daler Rowney Cryla brand, which like most things Daler-Rowney has never yet let me down.
Here is Robert´s website
Feel free to share your personal experience with us.