Project invitees can't access files

I’ve shared multiple projects with 2 of my colleagues (we all use personal accounts), and I’ve checked that their access rights are set to “can edit”. The projects only have Illustrator cloud files in them.

They can both see all the files in each project, but when they try to open any, an error message says they don’t have access.

I can only find answers about this relating to team/entreprise accounts, not personal accounts. How can this be resolved? Thanks!