Switch to any other household in the Manage World mode. Once you gain control of another sim household you should be able to build on any lot. Another option which i would not reccomend but will probably make the error message go away is to use the cheat that lets you edit your sims traits. Editing your sims traits will make you lose the traits you have learned through aspirations and careers but the error message will go away when using your main sim. Probably only worth doing if you havnt invested too much time into your sim.
Hope this helps and good luck.
Thanks, switching to a different household did help indeed. Worked like a charm! My kind thanks to you!
