Append to polygon doesn't work

[k.moonsXH6PH]

I tried to append to polygon to fix faces on my model but it doesn't work and I don't know how to fix it. Thank you in advance for your help.

[k.moonsXH6PH]

I just realize that my files weren't added

So here's my screenshot:

And I'll also try to add my file.

[_sebastian_f · Accepted solution]

it does not work because there is no hole. enter face mode, double click the model (to select all faces) and hit "h" to make all faces visible which got hidden. probably by accident.

[k.moonsXH6PH]

Thank you!