"Downloads will not be populated" seen in TSIM Install Log files where TSIMAgent & TSIMAdmin directories are not copied to TSIM Server.
These errors can be seen while upgrading TSIM to newer version or while applying Fix Pack (FP)
 

WARNING,com.bmc.install.product.bppm.server.postinstall.ServerPostInstallConfigUtilities,
  LOG EVENT {Description=[ <SERVER_INSTALL> D:\BMC Setup\TrueSight_Infra_Mgmt_11.3.04_Windows\TSIMServer\TSIMAgent does not exist. Downloads will not be populated.],Detail=[]}

The cause of the errors is due to leaving out the TSIMAgent and TSIMAdmin directory structures when installing/upgrading the TSIM.
In other words, don't only copy the TSIMServer directory to the TSIM to perform the installation; send the entire file downloaded from the EPD site.

To correct your existing installation, copy the following directory structure of a TSIM running the same version & Fix Pack to the TSIM where the error was seen:
<Install Directory>\pw\pronto\web\html\download\

Lacking such a machine, copy the zip files from the original EPD download. 

For example:
<Install Directory>\pw\pronto\web\html\download\win32_agent>dir
10/23/2017  11:12 PM       471,025,834 Admin.zip
10/23/2017  11:06 PM       391,075,925 TSIMAgent.zip

You would need to do this for each subdirectory in <Install Directory>\pw\pronto\web\html\download