Q.planted my patoes in very large container ,covered when an as plant growed watered as needed never over watered. when plants grown
to the top and abovethe top all was great they got about 20 ins high they started to blum and leaves started to die out and tubs begain to fold over .and became loose . i thought it was time to harvast and emptyed container and was nothen there at all.whats g oing on ????

Excess nitrogen can cause lack of tuber growth.
These articles will help you pinpoint the issue and hopefully next season will be more successful for you.
https://www.gardeningknowhow.com/edible/vegetables/potato/potato-plants-not-producing.htm
https://www.gardeningknowhow.com/edible/vegetables/potato/growing-potatoes-in-bags.htm