Block 'Question Mark' pokemon appearing

Hello everyone,
I started playing the game just recently. Wild pokemons are appearing as ‘??? ???’ with no name, no image just their sound effects (See image attached). At first i really thought it was part of the game to figure out or just the dark mode, but couple of hours in it is still persisting.
Also, the pokemons would only appear on screen when i caught them. (which got me into thinking that i should catch them all to unlock them all xD).

Anyone could help me, please! I don’t know if the emulator was not properly installed or anything missing in settings. And if i have to reinstall the emulator/ app, is there a way to save my ‘save file’?

Thanks
BKM
A Trainer

This occurs if the Mystery Challenge is enabled when creating a new save. This is not from normal gameplay; it’s meant to be an extra challenge for people who want it. If you don’t want this, you’ll have to create a new save that doesn’t have this challenge enabled.

but is there a way to save my previous save file?

Check your PC for an option to forfeit the challenge.