If they're in the area, they will eventually come.

I had the same empty lodgings for 2 years until a friend shared some of his cocoons.

Might search online for how-to info - in general, east facing where exposed to morning sunlight.

Start with this:

http://ext100.wsu.edu/snohomish/wp-content/uploads/sites/11/Orchard-Mason-Bees.pdf

And honestly, they might just not live in your immediate vicinity. Mason bees travel short distances only, and they are very picky about local sources of mud and local composition of soil -- if they're going to nest, they want the right materials nearby to minimize their work and maximize their time reproducing.

In western washington state, mason bees are widespread. But sites just half a mile away from each other can be vastly different in terms of performance.

If you buy bees, they hatch, and they all leave (or "disperse") then well, it's just your site, and no matter how great you make the house they just wont show up to the party. :-/ Best of all, they like clay-y mud, despise sand, and like a natural source of wet mud like a nearby stream bank or reliably wet area. No amount of putting perfect material nearby makes them change their mind :-)