I am brand-new to DnDbeyond, only ever used pen & paper. I created all four characters in-person with pen and paper. When digitizing them, one of the characters was immediately available to choose when joining the campaign. The other three are not showing up. I even made sure the Race, Class, & Ability scores were completed. Can anyone advise?

I wasn't able to figure out how to include images in this post (not tech-savvy, I apologize). When on the Campaign page, it only shows one 'unassigned' completed character. However, I created the other three characters using the exact same process, except I made sure to use the 'Create Character' link directly on the Campaign page to create the remaining three characters, and all are complete.  When following the invitation link, it shows the one character, followed by three "My Characters". I would like them as available options in the campaign. Please help!

You should be able to add those characters by following the campaign link, selecting one of the characters from the “my characters list and then clicking on the “join with this characters button at the bottom of the list of your characters. You will need to do this one character at a time. Once you have added the, all, go back to the campaign and click “unassign” under each of the characters, presuming that you want others to be able to claim them.