The Partner Source download functionality is currently in transition and you cannot download from the Partner Source site. The good news is there is a work around. Often you need to get a cumulative update for NAV, so here is how to get them during the transition.
- Sign into Partner Source (mbs.microsoft.com/partnersource)
- Find the update you are looking
- Note the ID for the cumulative update
- Go to support.microsoft.com
- Search using the ID from above.
- Select Hotfix Download Available