Have you been treating your hypo with fast acting carbs - not sandwiches, biscuits or chocolate as they are slow acting and can take some time to have an affect. but jelly babies, cola, fruit juice or dextrose.
I would be downing all the fast acting carbs hat I can find. If I run out of GlucoTabs, I would be raiding my baking cupboard for dried fruit.
And then following it up with slow acting carbs to try to maintain it.
As for the cause, have you had your covid jab recently? I spent a couple of days fighting off hypos after I had mine and was surprised because, up until that point, I had only read about people experiencing rises in blood sugars. Since then, I have discovered I am not alone - 2 weeks after my second jab and my basal is still 75% of normal.