What is the right time to give up?

It has been 17 years since I entered the world of wildlife conservation as a volunteer and then as a professional. I have experienced many hardships, joys, failures, and successes alongside the groups I have worked with. Wildlife conservation was never meant to be easy, let alone in a country that has been severely sanctioned for 50 years and has a totalitarian government.
Although we have often grown tired, paused, and then resumed, I have been thinking about this question lately: When should we give up? While we always fail, how far should we go and at what cost should we continue? PayPal recently blocked our account for receiving donations, due to sanctions. Also, Mailchimp, closed our account without any warning, solely because we are Iranian, without allowing us to back up the 20-year-old database of subscribers and recipients. Although humanitarian and environmental activities have never been sanctioned by the U.S. government, service providers refrain from cooperating with Iran. Worse still, they do not behave professionally or respectfully towards us, or perhaps we simply do not matter. Every year, the number of international organizations interested in collaborating with us decreases, and obtaining foreign financial resources has become almost impossible.
On the personal front, due to a lack of financial resources, we have always had difficulty paying salaries, and currently, not even one full-time employee remains for the Iranian Cheetah Society.
Thinking about a situation where the government has no interest in nature conservation, and we are under pressure inside the country, and while the Asiatic cheetah is on the brink of extinction, continuing seems impossible.
We met with rangers and local communities in the cheetah habitat. They are also extremely tired and hopeless. We tried to give energy to them, but in reality, we were also spending our last shreds of hope and energy.
A few months ago, among specialists in cheetah conservation in Ethiopia, among those who face much fewer and more solvable problems, I found about how meaningless the path we have taken seems. Even the cheetah conservationists asked us “Why do you still continue? You have no chance!”
Last week, after a problem arose with our PayPal account, I couldn’t sleep for several nights. The moment we received the final email stating that our account was being permanently closed, I thought about whether we deserved this level of failure, despair, and stress. How long should we endure all this and continue? Where is the stopping point? When, after various harms from all sides, our mental health is severely threatened and stress and pressure have taken away our ability to work, where is the END?
Now, I think more seriously about giving up, and I imagine that after all these years, we are on the verge of losing our beautiful cheetah and facing final defeat. Without hope, without motivation, and without a future.