Language Selection for menu not there (and no screen option also)

Hi there,

I have a pre sales question: I’m just checking out the free version of Polylang on two of my websites to see if there are any conflicts with other plugins I use (and I’m glad I found a problem so I can check out your customer service, which for me is also an important part of buying a software product).
I use a theme from ThriveThemes or the GeneratePress, Contact Form 7, WF Cookie Consent, and the ThriveThemes page builder and Thrive Leads.
So all pretty standard, or do you suspect any potential conflicts here?

Strangely on one of the two sites I have an error / bug that I don’t have on the other although they are set up exactly the same:
Generatepress, Thrive Page Builder, Thrive Leads, WF Cookie Consent, Polylang.
It’s the problem described here:
https://polylang.wordpress.com/documentation/frequently-asked-questions/the-language-switcher/
I can’t add the language switcher in the menus
In appearance->menus, go in screen options on top right of you screen and check the “Language switcher” checkbox. You then should have a new metabox which allows to add a language switcher just as you add another menu item.

Well, I don’t have that option in one of the two sites (BTW: They are not live yet, so I can’t provide links). On one of the two sites everything is working as it should, the screen option is there, the language selector for the menu, everything. On the other – exept for the domain name exact same WP install – it’s nit there, nor the screen option where I could activate it. I deactivated all other plugins, I deinstalled Polylang (with and with out erasing the polylang data), the menu language selector is not there, only the language selector widget.
I hope we can sort this out, as otherwise I really like to purchase Polylang if it functions as great as on the other page I tried it on…

Thanks,
Andi