I think when yours leveled up to level 40, you probably made him faint, so it didn't evolve. Try to make him level up one more level, then I think he will evolve because level 40 is when it evolves.
If that does not work, it might be holding a everstone. Take it then level it up if that's the case. Hope it works!!!
ponyta evolves at level 37
Ponyta evolves at level 40.
ponyta evolves at level 40
A Ponyta evolves on level 40.
Ponyta evolves into rapidash at level 40.
A fire stone might work, but ponyta's usually evolve at level 40.
Train it more in the morning.
ponyta evolves at level 37
Ponyta will evolve into Rapidash at level 40. -Hope this helps!;)
Ponyta evolves at level 40.
ponyta evolves at level 40
ponyta evolves at level 40
Ponyta evolves to Rapidash at level 40.
Level 40
A Ponyta evolves on level 40.
Ponyta evolves into rapidash at level 40.
no ponyta cannot evolve with a fire stone, you need to raise it to level 40 and then it will evolve