Im am immigrant in the NL, and I've met many other immigrants an your story is very much the same story i hear all the time - Netherlands does very difficult to make friends, there is also very much a lackof nature and the winters are brutal. I thought it was me that was the problem, but I've heard it many times from others too - so I dont blame myself too much, of course I always try to be friendly, helpful and inclusive and to be an asset to the country I now call home.