Zoom Webinar trouble with interpreter

[Munich]

Dear Community,

I held 4 Zoom Webinars with interpreter last week, 1 of which, no. 3, went so wrong that I had to cancel it before it even began.

I had set up an interpreter, but she could enter as panelist only, I wasn't able to give her the interpreter function, and the Zoom popup told me that the interpreter (i.e., her) had not entered yet.
I then asked her for an alternative email adress and additionally entered that email adress as interpreter, and she received the invite, entered with that second email - same issue. 

The next, and last, webinar then went smoothly, with the same interpreter and her same email adress (the one I had used originally in the webinar that went so wrong).

I have no idea what caused the issues in no.3, since I used the same settings on all four, as far as I can see. 

I scheduled these meetings for my colleague, he was moderator, I was alternative moderator. 

The interpreter told me that the invite (for the webinar that went wrong) was unusual, it began with "Helloname", instead of "Hello Name", the space between hello and her name was missing.

I am currently using a trial version of webinar.  Could this be the cause?

In a few days, I will be having a substitute for the webinar I had to cancel and I'm a bit nervous, especially as I wasn't able to find out what caused the issues in the previous one.  

Thank you for your input!

[Munich]

[I clarified in the original post]