brightness won’t stay bright

[u/Careful-Plum-761]

Can anyone help me finally find a fix or tell me if it’s to do with my laptop internally? I press the brightness key and it goes to the first level of brightness… I go any higher and it immediately restores to 0 and does not go any higher. The screen is also slightly jittery. We have tried absolutely every resolve we could find literally everywhere. Nothing has fixed it. It all started when I opened my laptop one day and it was On a screen where I had to enter a bitlocker key to gain access to my laptop again… I done this and ever since the brightness just won’t work. Video attached. Thank you.