I try to push on smartbit.com.au and I get PUSH TRANSACTION ERROR: 64: NON-FINAL
There's only 2 reasons I think this error could occur:
1. You added a space or extra character somewhere that it wasn't expecting so it couldn't parse it
2. It's just broken. I'm leaning towards the second.
3. Also was it definitely past the blockheight? The 10 minutes if you did use blockheight might be out as the 10 minutes is a targeted average.
There's also a chance the fee was too low. That seems to be a common error and a lot of nodes used to not hold.more than 20mb in their mempool (but I imagine these explorers could hold at least 128gb in their mempool without exceeding the capacity of a single ram chip.