So my issue is this. I am a GM and have created a new spell for one of my players who is in my campaign. The spell is published and in my collections. Content sharing is turned on for the campaign and the player has "Homebrew Content" activated. But this spell is still not appearing. Even when i go in and manually try to add it, it still isn't showing up. So i am curious as to what am i supposed to do? Or is this something out of my control? Please help. 

More than likely you've set the spell to one version of the class but the player has chosen the other version of the class.

For instance your 'Conductive Vapours' spell was made available for the 2024 versions Druid, Wizard and Sorcerer. The player may have instead selected the 2014 version of one of these classes instead.

Since you have shared it publicly, you can no longer edit the spell. The recommendation is to create a new version of the spell and add the 2014 version of Druid, Wizard and Sorcerer in the Available For box. 

I will also add a general note: you do not need to publicly share homebrew for your players to select it. Any homebrew you create is automatically shared with everyone in the same campaign as you with no subscriptions of any kind needed by anyone. It is recommended you fully test and check the spell is as you want to be and working fully before you share it publicly. 

I am kicking myself for not thinking about that. Thank you very much for your help.