May not be marked as polarized but, it has a VDC rating and it seems to be (best I can read the traces) connected (with its 400VDC mate) to a negative lead of one of the three 626(?) diode/(rectifier)s.
If it were me (and it's not, of course), I'd replace it with a stock 220uF, 250V (or higher) electrolytic and see what happens.
Try to find a replacement that, at the least, has similar physical dimensions since this is a rough indication of voltage level tolerance and, as a result, energy density. Pin placement may have to be accommodated by jumpers.
I'd put the negative lead to the trace with the elbow (45°) bend and a white dot (a via?) with "C1" beside it.
Wear eye protection during the testing of the replacement.