This happened to me several times. So far, I have not had trouble collecting from the houses or the Steel, Planks, or Marble. The level 2 workshops have not had this problem; only the level 1 workshops. It APPEARS to collect, but it doesn't; the hammers still appear over the shops, and when I click, the progress bar shows that it is ready to collect, but I can neither collect nor order anew. I may have found a temp. fix: When I fill out a support ticket to report the issue, then go back to the city, I can then collect. Nothing else (clearing cache, visiting another city, waiting for houses to spot out cash in 5 min, reloading, turning computer off then on, does not fix it; only reporting it. I know that it was not fixed by the support team, because there just was not enough time to have a game mod fix it after I reported it.