Cannot fill out “dropdown” registration field

Hi!

Two persons interested to register as members (at least one of them using Explorer) are telling me that they are unable to fill out the “dropdown” and “multiselect” fields in the registration form. I am on a Mac and have tried registering on Safari, Chrome, Firefox and Edge Dev – where there is no problem – so it seems that the problem is for those using the Explorer browser.

Any ideas what to try to resolve this issue? At first I thought it was because I had not updated to version 2.1.3., but now after I have made the update I’m told that the problem is still there.

Many thanks in advance for any assistance you could support with!

Cheers,
Annica