Q: Why won't BOINC download more Rosetta Work units?

A: It is possible the servers are down for some reason (quite rare). You should check the server status.

But it is more likely you are seeing a message in the BOINC Manager saying "...not requesting new work". If so, then your PC is actually not asking for more work.

If you are running multiple BOINC projects, the BOINC manager plans out what will be crunched next, and balances goals like the deadlines of the work units, and your preferences as to resource share to devote to each project. In this balancing act, it sometimes crunches a project more than it's normal share in order to meet a deadline. When this occurs, the project being crunched incurs a "debt" to the other projects. BOINC will take this debt in to account when requesting new work. It is not uncommon, especially when running 3 or more projects, for BOINC to decide to crunch other projects for a period of a day or two in order to pay back such debts. And so during that time it will not order more work for projects that it does not plan to be crunching for a while.

In the end, if you leave things alone and resist the temptation to try and FORCE BOINC to do work for a specific project, it will work itself back in to balance and again download work for each project.

If you want to increase the resource share for Rosetta, you can increase the value in your Rosetta preferences, and then update to the project. You can view the present resource share in the Projects tab of the BOINC manager. The BOINC Wiki has more discussion of how resource share works.