First of all see T's solution and make sure that the freesat box has two feeds.
On the FOXSAT-HDR increasing the number of feeds to the FOXSAT-HDR from one feed to two feeds will not alone resolve the problem.
The FOXSAT-HDR will only use the second feed if that second feed is in place during what the manual describes as 'first time installation'.
After connecting with a second feed selecting 'default setting' on the menus will force another 'first time installation' and the second feed should now be recognised.
See the following link for details by Graham L Thompson of what appears to be an alternative and easier method of forcing a Humax FOXSAT-HDR to switch from a single feed to a dual feed: http://hummy.tv/forum/threads/workaround-for-failed-freesat-tuning-with-zinwell-quad-lnb.1113/#post-13927