I've a couple of Oxalis that seem to have stopped flowering.
One is a self sown hybrid of South American species - it's now in a 5 inch pot, lots of leaves, no flowers. It used to flower really well, even though it was under the greenhouse bench - this year it's been in a frame and then into full sun outside maybe it's age or they need to be divided?
Edit: I recall now it didn't flower last year either - I thought at the time it might have been because I repoted it the year previously. I should add I have smaller plants of O.patagonica and O. Ione Hecker given the same treatment that are flowering fine. The hybrid is a hybrid between those two.
Similarly I have a O.obtusa in about a 9 inch pot - there must be lots of tiny bulbs it's absolutely packed with leaves - but no flowers this year.
Come to think of it O. versicolor didn't flower either but that's no where near filling it's pot as its only a couple of years from a few bulbils (but it flowered last year).
Ideas anyone? thanks