ᐅ Wood stain still sticky after 2 months

In mid-September, I sanded my wooden windows made of Framiré wood, treated them with Aqua Clou wood primer, and after one day of drying, painted them with AQUA CLOUsil wood stain (both newly purchased).
Now, after 2 months, the windows are still very sticky! One window is difficult to open.
The manufacturer is not providing any support.
What can I do to remove the stickiness?

Did you mix it well?
What does the manufacturer’s expiration date say?

.. too thick layer of paint?

Yes, I have checked thoroughly. The primer and stain were purchased in June 2020. I don’t think the paint was applied too thickly.

My question is, what can I do now?

If the manufacturer is actively on Facebook, try contacting them through that channel. Usually, the page administrators have a different level of access to customer service since their role involves protecting the company’s reputation. For me, this approach worked with Grohe, for example.

I contacted the manufacturer by letter after two unsuccessful emails. Then I actually received a call, during which they said: it must be due to the primer, so I should wait longer.

After two weeks, I am still not convinced.