spam lp
keyboards are not good at handling multiple key presses simultaneously.
Some keys share circuits, and if the keys you are using for b+lk+hp share a circuit, they might not all be registering. Every keyboard is different, but some keyboards will beep if you are inputting incompatible keys at the same time.
Also (and I’m just a newbie, so take it with some salt) here a few thoughts that are easy to use, and have helped me a bit.
When in any other move (block reaction, get up, jump attack etc…) I spam lp, then all you have to do is press b+lk+hp to ultra if the opportunity presents itself. That way you are timing just one input instead of 3.
You can actually input the lp’s during a block reaction without jabbing, then wait for the b+lk+hp to get the timing right if you are punishing a shoryuken. You can’t wait too long, but there is a bit of a window that allows you to hide the lp’s in the block reaction and still fudge the timing of the final inputs.
If you have the lp’s setup, it’s like pressing 1 button to do the ultra, so you can be a little more exact on the final input, or decide not to do it.