Cash Available Declined Order

Yesterday I had this order get declined. I want to make sure I fully understand what I am doing wrong especially since so far today it is a painful trade to not have made.

My software often sends sells and buy orders at the same time, but I put a delay on the buy orders of 60 seconds. This way if the purchase needs to use any of the proceeds from the sale of a previous security it is able to do so. So all my sales occurred yesterday at 3:50 pm. My purchases should not have gone through until 3:51 PM but they were cancelled due to a lack of purchasing power at 3:50 PM. By my estimates from my data logs etc. I should have had about $33,750 at just before 3:51 PM in cash then had about $33,700 in orders for ZIV and UPRO, but only ZIV was filled due to lack of cash on UPRO.

Can a C2 representative look into it and let me know if my delay method is not sufficient to do what I want or if I am just incorrectly calculating my buying power that C2 gives me etc.? For now my fix is to just increase the cash holdings to prevent this from happening again and I have extended the buy delay to 120 seconds.
@MatthewKlein

Do you get a log confirmation of the SALE with a timestamp? You cant confirm on your end?

Currently I don’t have a way to show a log of my C2 buying power and don’t know if a way to do it. Again I think my fixed will prevent the problem in the future but if I can dial in the software I would like to hold less cash.