Follow is not one of the round buttons in the right-hand column. Those five are Like, Save, Comment, Share and Report. Follow Project sits in the more menu, the three-dot control on the bar directly beneath the project's media.
Open that menu and choose Follow Project. It becomes Unfollow Project once it is on.
The control is not offered to everyone
Three things remove it, and none of them says so.
- You are on the project's team. Owners and credited members get Edit and Delete in that menu instead. You cannot follow work you are already on.
- You are signed out. The media block asks you to sign in, and the engagement bar is part of that block, so it is not on the page at all.
- You have no active membership, or your free views for the month are used up. The same block is replaced by an upgrade message, and the bar goes with it.
So a visitor who can read the project can still be unable to follow it. See Which parts of a project page disappear when you are not a member.
What following a project actually gives you
One notification, when that project is published. Nothing after that. It does not notify you about new versions, new comments, awards the project wins, or anything else the team does later.
That makes following an already-published project close to pointless, which surprises people who expect it to work like following a person. If what you want is to come back to the project later, use Save, the bookmark button in the right-hand column. If what you want is to hear about someone's new work, follow the person instead. See Following people, organizations, topics and work.