www programming

I thought I had to upload it into the file where I uploaded my phpBB3 files. I've now uploaded into the public_html file, which should be the root folder, which is before the folder where I uploaded my phpBB3 files in. Still the same problem though.

no you did not because if you click this link it return file not found:
https://talkatastic.be/forum/iframeResi ... dow.min.js

you need to load this file, may into
public_html/forum
that's folder where you installed phpBB, so the phpBB relative root

p.s after, check also that if you are in https into wp (because you wp main url setting is set with an url with https), then you should setup phpBB to force https intp ACP, or if you login as http into one, and after the other is under https, you'll experience problems on result logged in

[EDITED]

I'm most certainly sure it was uploaded there:



Okay, I'll have a look into that.

EDIT: Okay, something weird is happening now. The wordpress forum page keeps refreshing automatically. I have to go now, so I can't look into it for now. But I'm not sure what caused this.

so, it has been uploaded into folder, with wrong permissions into file?
Can you setup it as chmod 666 or what chmod your server let files be readable

I'll look into it when I'm back.

Something weird is happening now. The wordpress forum page keeps refreshing automatically. I have to go now, so I can't look into it for now. But I'm not sure what caused this.

since you are under http, and not https,
now change last line added into overall_footer.html, to point to and not or force as said both wp and phpBB to be under https