You first say:

Posted by: Robert

The correct is "/" not "\"

then:

Posted by: Robert

create one with this key:

This topic doesn\'t exist or you don\'t have permissions to see that.

So, please, which one is the good one? Slash or antislash?

Thanks

This topic doesn\'t exist or you don\'t have permissions to see that.

Also try using Loco Translate plugin

Thanks for your last answer, but this does not work either (phrases cache deleted). Also, this phrase is not in the wpforo-*.po file.

So, how can we fix this please?

Please try to add the phrase key with a backslash (\) like this:

You don\'t have permissions to see this page, please register or login for further information

Also please don't forget to delete phrase caches (Dashboard > Forums > Dashboard admin page) before checking. 

I have the same issue. I've already used Phrase System adding a new phrase exactly copied and paste "You don't have permissions to see this page, please register or login for further information" but it doesn't work.

I noticed that there are "strange" things about "don't", seems to be written "don'/t", isn't it? 

Anyway, why nothing changed even if I've added 2 new phrases with "you don't" and "you don/'t"?

View files attached please.

Thank you

Riccardo