Hi ​@Frank61337 - Just to confirm, are you accessing Outlook from a webpage or through the Outlook app? You mentioned you selected the calendars in outlook.com so I just want to be sure.

The next thing is making sure all of your events are marked as Busy, this ensures Calendly can detect your events correctly.

Let me know - I can investigate further from there.
 

HI David, I am accessing Outlook via the program (app) installed on my laptop (in hinsight probably not .com). 
In Outlook, all my activities are standard marked as "busy".

Enclosed the picture that I get from the Calendly overview of calendars to check.
So wondering what to do with this.
 

Hi ​@Frank61337 - Thanks for sending this over.

In this case, I’d want to check some of the settings in the plugin directly. I put together an article that walks you through some items to check here:
 

Once these are checked off, you can go back to your Book Meeting page and override available times to see what events Calendly is picking up:
 

Let me know if this works!

HI David,

I followed the instructions and got my calendly settings right. Still it doesn't synchronize, stating it needs a plug-in key.

(In the descriptions I saw that this doesn’t work with outlook bought from the Microsoft store; I'm not sure where I bought my MS office package in 2017 though).

Can you hep me to get a plug-in key?

with kind regards,
Frank

Hi ​@Frank61337 - Thanks for reaching out.

You should get the plugin key during the process of installing the plugin.

Did you receive a link to download the plugin? I would try going through the download steps again, then you should see a page like this:
 

Let me know if this works!

HI  David,

The above screenshot is familiar. I can get to there, but I didn't get a link to get the plugin. (Or missed it somewhere when I took a paid account 2 weeks ago).

Can you tell me how to get this?

Hi ​@Frank61337 - You can get a link to the plugin from the Support team, unfortunately its not something I can share over the community.

You can email them directly at support@calendly.com or by chatting in for quicker assistance. They’ll be able to help you from there!