Share Screen

Are you the meeting host?

It is located on your profile page, if you are host.  On Schedule a Meeting, select the option for Video On.  This button is located at the bottom of the Schedule a Meeting page, right above Options.  You can select this option for host and participants, if you wish.  It defaults to no, so you need to check it before each meeting to be sure.  Hope this helps.

@dkjonsson  First. can you check if Screen Sharing is enabled to your account by clicking your profile Picture - Settings - Scroll down, View more settings - In Meeting Basic - Screen Sharing - Toggle on the radio button

Second, Like what you said, you are trying to share a PPT presentation while in a Zoom Meeting.  Even when using a Basic or Free account, you can still do a screen share. 

Here is the only Restriction: For Basic accounts, screen sharing is set to Only Host by default.

https://support.zoom.us/hc/en-us/articles/201362153-Sharing-your-screen-or-desktop-on-Zoom

Please also check the Prerequisites for video conference sharing: 

• Zoom desktop client
  • Windows: 5.0.0 or higher
  • macOS: 5.0.0 or higher
  • Linux: 5.0.0 or higher
• Zoom mobile app
  • Android: 5.0.0 or higher
  • iOS: 5.0.0 or higher

Lastly, you may want to check your Share Screen settings by clicking your profile Picture - Settings - Share Screen and see if the following are checked properly: (You can customize the right settings for you)