Tennis federations have no power to give visas
That is correct.
I meant to say, the national tennis federation, when they agreed to the contract with ITF, should make sure that their country does not exclude ITF member countries players
And how do you know these werent't extraordinary circumstance (and who are you to say when a country can or can't deny a visa??)..
I don't know. I read the article in the link, there is much in the way of explaining why the visa was refused.
The interesting is the same article stated the Israelis routinely get visa thru a third country to travel to Venezuela, so there must be something particular with this case.
The article also said, the player and her coach started the process of securing the visa 3 months before the tennis event
The visa issue is 100% out of a tournament's control. Maybe the burden should be on the ITF to avoid granting tournament licenses to "trouble" countries rather than on tournaments to ensure visas for players, which is impossible.
I agree, but I think they do not engage in direct negotiations with the country government, but with the national federation.
The national federation is in better position to know what their country law allows or does not allow.
Based on that they make judgement whether they can meet the contractual obligations set by the ITF