Embedding calendar problems

Hello, I am using a free wordpress blog
(url: https://abudhabidaysblog.wordpress.com/ )

I used to be able to embed google calendar in one of my pages (using a simple iframe string in the ‘text’ bit) but now when I try to do it, all I see is a big grey box with what seems to be a ‘play’ button in the middle. I also tried with the TeamUp calendar embedding string but the same thing happened.
I am 100% sure it worked when I tried it a few months ago, so I don’t understand what can have changed.
I tried to update my Firefox etc but it did not solve the problem.

If you have any suggestion (in a ‘for dummies’ language, please!), I would be most grateful!

Thank you very much in advance :):)
Laura