Can't interact with house

@escapedpolarbear  Alright, then it's time to try evicting your own sims and bulldozing and replacing their house, as described above.

Will this cause all my furniture to be lost... because I am planning on moving soon, so should I wait?

@escapedpolarbear  No, this shouldn't delete any of your furniture.  And it's completely different than moving.  An in-game move won't reset your sims in any way or get rid of the potential corruption in your game.  The Edit Town evict/bulldoze/replace method will, although it's not foolproof.

As always, if you've made backup copies of your save, you can always revert to one of those should you not like the results of one of these troubleshooting steps.

OK thanks; I'll try it. I'm trying this all on a duplicate saved game - thanks for suggesting that!

The 'no interactions available' thingy has gone now by the way - I can visit the Langeraks properly.