LG G2 can't get into recovery mode

[mickyinz]

I rooted my LG G2 D802 with stump root with the intention to install lollipop. But ever since I can't get into recovery with the press power volume down buttons. I have unrooted in supersu so the phones not rooted at the mo but I can't upgrade my rom.
The phone is working normally but I would like upgrade after pressing power volume button goes tries recovery screen but goes into error and then off so keep power button on for a long time and it comes on as normal again.