Hey Decisive_Gaming,
Depending on your past selling record, i.e. how many items you sold through your Gameflip account and what types of items you are selling, your cash from sale proceeds could be held for a few hours to a few days.
As you establish a good selling record over a period of time, the amount of days that the cash from completed sales is held will be reduced and may even be instantly available.
The information above can be found in the following link 
Also, I see in your account that you recently sold forbidden Gift Cards!
Please read the following link and see the currently allowed non-gaming Gift Cards:
