Saflager appears to have an ideal temp range of 53-59f. And is rated 48-71f.
Looks like you fermented on the cold end. Yeast will work much slower and some will go dormant.
Also after fermentation it's a good idea to warm the lager yeast up to room temp 68-71f for 3 days for a diaxetyl rest this also helps achieve final gravity.
After those 3 days lager it nice and cool for an extended period.