Seasoning refuses to stick to carbon steel pan. Tried various techniques

Before you go scouring your pan with steel wool.

When you said you followed the instructions, did you follow the manufacturer's instructions, or some other website?

Because although random websites might have good advice on building up the seasoning, they don't know how the pan was treated by the manufacturer, and what needs to be done to remove the protective layer that they put on it.

As you said this is a Mafter, their instructions are on the warranty page:

Black Steel Frypan Seasoning

Before the first use – Place the frying pan under hot running water for a few minutes, to remove what remains of the protection layer, with a brush if necessary. Dry the frying pan, then fry in a portion of oil, slices of sprinkled potatoes, and large portion of salt for a few minutes. Discard contents, then briefly reheat frying pan with a little oil, remove from heat and wipe with paper.

After use - Wipe with paper or if necessary rinse under hot running water. Clean without dish washing liquid. Dry and re-grease lightly.

Pan and Blue steel Preparation

Do not use pans or new molds before under going preliminary treatment. Pans and molds must be warmed in a temperature of 230º F to allow a good hot cleaning with a cloth. After they have been cleaned with a cloth, they are put back in the oven, one of two times more, until the cloth has very little soil left. Then the pans or molds are greased with vegetable oil of quality and subjected to a temperature of 390 degrees F for two hours. You have to clean them a second time with a cloth, then grease them. Now they are ready for use. The greasing must be repeated before each use.

Reminders

The blue steel molds are sensitive to dampness. Do not stock in a humid environment, such as a cold room. You must clean with a dry cloth. DO NOT use an abrasive sponge, it could damage the upper coat of metal, which would lose its properties. Washing is not recommended, however, if a wash is done, you have to dry and grease the molds or pans immediately according to the process described above.

I knew the source of your problem the second I saw "flaxseed oil". Been there. Done that. It seems to either work for people or it does not.

For me it did not. Tried it on several pans and the result was it formed a coating that flaked off like varnish. I wound up stripping it off said pans and re-seasoning them (successfully) with different oil. Two of the original failures were Matfers, by the way. They are fine now after I seasoned them with something other than flaxseed oil.

I did them on top of the burner on a gas stove, by the way, not in the oven.

This was posted a long time ago. I hope the OP stuck with it, because they would probably have a nicely seasoned pan by now. I think some people may simply be giving up too soon. I find that carbon steel takes longer to season than cast iron....like months....so, I would not worry too much about it. Just use the pan. It will continue to get better. Just be careful when cleaning, so that you don't clean off any seasoning layer. I mostly just wipe my carbon steel with paper towel. When there are stuck on bits, I use a plastic scraper, or a very gentle scour pad. The best approach is just continued use over time. Be patient.