can't sync external calendars together

Hey there, @Giuseppe87674 - thanks for posting! Firstly, check out our New User Guide - it’ll def prove helpful as you get used to the platform!

To be clear - are you attempting to get your Google Calendar and Outlook Calendar to sync with each other so that you can connect just one to Calendly? If so, I can help! Or, are you attempting to connect both calendars to Calendly? I can help with that, too! 

Navigate to your Calendar Connection page from the drop-down menu on the top right corner of your page.

Select which type of calendar you will be connecting. Calendly integrates with the following platforms:
Google
Office 365 or Outlook.com
Exchange
 
Once connected, take a look at the settings on your Calendar Connection page.

If you have connected more than one calendar, use Edit to choose which you would like Calendly to check for conflicts. Any events labeled busy in the selected calendars will be read as conflicts, and those times will be removed from your scheduling page.
You can also select which calendar you would like your Calendly events added to. When an invitee chooses an available time to meet with you, the details will be published to your connected calendar and the Scheduled Events tab on your Home page automatically.
 
Note:
You can only publish events to one connected calendar.

That last part (in bold) is important given what you stated at the end (that you are attempting to get your Calendly bookings to appear on your external calendars). You will only be able to view your Calendly bookings on one external calendar, the “add to” calendar that you select after connecting your calendars. 

If you’d like to see your Calendly bookings on multiple calendars (Google and Outlook.com/O365), you’ll need to share those calendars with each other (which is not a setting that Calendly controls). Here are some articles about connecting your Google and Outlook/O365 calendars: 

https://support.microsoft.com/en-us/office/see-your-google-calendar-in-outlook-c1dab514-0ad4-4811-824a-7d02c5e77126

https://support.google.com/calendar/thread/228933623/how-do-you-sync-an-outlook-calendar-to-google-calendar-on-an-android-phone?hl=en

If you run into issues doing that, please consider reaching out to Google Calendar and/or Outlook/O365 (Microsoft) support here and here. 

I hope this helps! If you need anything else, please let us know! =)