How to deal with an unsupportive SME ?

Hi Eirik and welcome to the community!

Having a SME who isn't that engaged with a project is a rough situation, and definitely one I suspect many people in our field have experienced at some point.

Assuming both you and your SME are internal employees at the same company, what can help improve this situation is going to depend a a lot of different factors—from your relationship with the SME, how much their input holds up the project, what other stakeholders are involved, your relationship with your manager, and the project documentation.

So there's unfortunately not one approach that always works. But I can share some things that have worked for me in the past that you can try mixing and matching for your particular situation.

• Find a different way to connect with your SME. Sometimes it's less that they have no time to collaborate, but more that the collaboration method you're using right now is something they have trouble with. If a scheduled meeting doesn't work, maybe asynchronous collaboration would be better. Or switching from digital reviews to paper ones? Or collaborating via Slack or phone. Ask them if there's a different approach they find easier to fit into their busy calendar.
• Be upfront with the SME, your manager, and other stakeholders about the impact of these delays. If this is starting to seriously impact your ability to deliver the project on time, loop in your key team members now and start talking about alternative solutions. Maybe the SME doesn't realize how much this is impacting the project timeline. Or perhaps they thought they'd have time to contribute but then got swamped with other projects. Whatever the reason, the original plan and timeline isn't working, so you need to all decide on a new way to move forward.
• See if you can bring in a new or additional SME. If your current SME is legitimately too busy to give you what you need, this could mean you need a different SME. Alternately, you could always lighten their load by splitting up the work across multiple SMEs instead of just one. That way each SME's work on this project is easier for them to manage.
• Negotiate with your manager/stakeholders for more time. If this person is the only SME you have available and they're critical for the project, you may need to talk with your manager or stakeholders about changing the project timeline around this delay. If you do this, definitely get the SME to agree to the new timeline in writing, or else you could easily get delayed again.

Hopefully one or more of these approaches can help turn this situation around for you.

And while it won't help for this project, in the future you can avoid some of these SME delays by starting every project with a kickoff meeting and written project plan where everyone involved in the project agrees to timelines, deliverables, and what happens if there are delays. That documentation helps SMEs see how important meeting their deadlines is to the project. And it also gives you agreed on next steps if a delay happens anyway.