After closing tablet I restarted game, used menu to take me to a different house, one that had a pool. Message came up again but after clicking on it several times it stayed off for lo n g enough for me to click on the pool and send a SIM to clean it.
Then returned to house where problem started. Clicked on message, it took about eight clicks before I could click on pool and send SIM to clean it. As it was a complex pool, like the one in your screenshot, I then sent a second SIM to clean the other end of it. In my house there was a second small pool so I bought in a third SIM and using the same repeated clicking method set them to work cleaning the small pool.
Hope this is of help.
