Originally Posted by f0zzyNUE

that's a known issue - but the same with other frequent flyer programs, airlines don't provide many awards (especially business class) to partner programs. hence most of the time you get no availability (especially on popular routes)
you can try searching in other programs like LH or AV to see if these programs get award seats from other *A airlines.
last resort - call M&S hotline - the agents might have a better tool to search for available awards.