I've used the interlocking fingers technique - interlock the fingers and slowly draw them apart while looking at/beyond the space where your fingers were - but I was taught to do it against a white background.
I started to see strands of 'chewing gum' between my fingers, then started to see colours. I used to practice this when I was in the toilet, as it had the only white door in the house

It was my sanctuary, in more ways then one.
Sweetpea, you have this ability still, maybe it needs to be coaxed out of hiding. And trust yourself that you can do this. It's a case of remembering how to do it. If you feel comfortable then talking to your angels & spirit guides and asking their assistance may help too.
Let us know how you go hey?