Hello Hakon,
Thanks for your email. Please make sure that those products are assigned to the needed categories. If yes, then also make reindex.
Please specify what do you mean under checking them as online only ? Changing product status to active?.. If you want products to show on storefront then their status should be checked and have +stock(depending on backoffice settings, products show due to their availability amount).
What about Mass Changer - did you change status this way? https://www.screencast.com/t/HElrCEw1
Other way to change product status is to export needed products ID and Status column, then change status value to 1 and import file back using option Modify Only.
If the issue remains, please contact us on our email contact@emagicone.com or in a live chat for further assistance.