I once had most or all of the symtoms of hypomagnesemia, and to finally retain magnesium it took experimenting with several different forms over many months and confirming it with testing. Daily Mag-hydroxide brought some success, then i added small amounts of Mag-sulfate throught the day, in coffee and juices. It still feels fantastic.
I've since replaced Mag-hydroxide with Mag-bicarbonate and drink small amounts of it 3 or 4 times a day, it tastes similar to mineral water. I was thinking of adding a little Potassium chloride and Calcium to it but am unsure how it would all react together in a liquid or if absorption would be reduced ...
Edit: and i had meant to say that i had been taking Magnesium on and off for many years prior, but things still went wrong for whatever reason(s) ie; dose size, consistency, forms taken etc.