OpenCart Community

I put my stock quantities in as 1000 I check that they all say 1000 then when I go back half an hour later they are all showing 0 nobody can order anything because the product appears to be out of stock. I had the stock set to 2-3 days now I have changed it to in stock. What am I missing?
I have searched for the answer and can not find anyting.
TIA
Alice.

Are these stock items with options?

Thank you DrSnake, to clarify, I understand how to use options, the options quantities most of my products have options but not all and the and that is not the problem. some of my products have options but not all of them, the problem is with the actual stock quantities changing. I know that sound bizarre but it is in-fact what is happening, I add a quantity of 1000 straight into the database, I check in the oc admin and they are all showing 1000 then I go back a little later and they are all showing a stock quantity of 0. I have done this several times the actual quantities of the stock are changing from 1000 to 0. However, I have managed to fix my problem by checking yes for stock checkout in settings.

I wish time were taken to solve all these bugs. Truly solve them.