Your teacher was wrong to correct you. 'Effort' can be either countable or uncountable, and your sentence is fine (apart from the 'on). Your sentence could be written as you did: "...I haven't even tried to make an effort to meet you there..." or "...I haven't even tried to make any effort to meet you there..." The first uses it as a countable noun ( a single attempt), while the second uses it as a uncountable noun (an abstract capacity or resource that you tap into). Both are equally correct, but I prefer your version. In fact, I'd say that the countable use of 'effort' is probably more common than the uncountable use. It's certainly more common when positive, for example : 'He made a great effort to understand the problem'. The uncountable form, 'He made great effort', sounds over-formal, and I'd probably correct that to 'an effort'. If a student has tried hard with a piece of work, the teacher might describe it as 'a good effort' ( as in 'attempt') - clearly countable. And, of course, it can also be plural ('Despite my best efforts') : this makes it extremely obvious that 'effort' can certainly be a countable word.

I know that everyone else (except your teacher) is saying that "effort" can be countable, but I'm not so sure. :) Surely, if you can only ever count "one" of something that's not really counting. If there can be zero or one of something then that might as well be uncountable. I've never heard anyone count "three efforts", or "forty-two efforts". But you do hear sometimes things like "they were making efforts to have the law changed" (but a figure is never put on how many efforts; presumably one per effort-maker). Pluralizing "effort", and using it with articles, doesn't feel to me like sufficient reason to believe it to be countable. If anything, we're talking about a very degenerate case of being countable (you can count up to one, sometimes one-per-person to give the illusion of plurality, "effort") or else an idiosyncratic way of talking about the uncountable concept of "effort". Just my two cents. :)

Hello, I don't want to say that your teacher is wrong. However, when I use "Effort" I use it the way that you see it in that sentence.

Effort is both uncountable and uncountable with difference in meaning. Yet, you don't ask a question with the word like "How many efforts.....". It is rather "How much effort....." "make an effort" is correct.