The founder of the Ahmadiyya Muslim Community, Hazrat Mirza Ghulam Ahmad (as) made many prophecies, and all of his prophecies were fulfilled. Sadly, there are allegations raised on his prophecies in the same way other prophets were also mocked over their prophecies. Till today, opponents of prophets raise allegations on prophecies of Prophets.
The anti-Ahmadi Muslims say that there is a prophecy in the book Nishan-e-Asmani (A Heavenly Sign) Page 14.
The opponents completely lie about this passage and misquote it. The revelation and prophecy of the Promised Messiah (as) is eighty years or thereabout. There is a typo here in the footnote which the anti-Ahmadis clearly see. It should translate to eighty years or thereabouts, and not forty.
Anyhow, in the passage of Hazrat Mirza Ghulam Ahmad (as) he clearly states “And it is Allah Who Knows Best”. The prophecy was about his age, not about the forty year mission beginning eleven years ago!
The second revelation which is commented on is not even the revelation of Hazrat Mirza Ghulam Ahmad (as) rather it is the prophecy of Shah Nimatullah Wali (rh) and it mentioned the mission of the Messiah being forty years. If we count this from the first revelation of the Messiah, it is fulfilled.
The prophecy of his age was fulfilled and even the opponents accept this. See the following link : https://ahmadianswers.com/ahmad/allegations/prophecies/age/