Could I lose my winnings from a bonus?

Yes. If I've read and understood your question correctly, if you've claimed a free no deposit bonus, there will most likely be a Maximum withdrawal limit. Let's say it's 500 and you've wagered the bonus at 7000. 6500 will usually be automatically taken off and you'll be left with a balance of 500. You can keep playing with that but you'll not be able to withdraw anymore than the 500, you can usually withdraw less though. 

If this existing player bonus was a deposit bonus, and you've kept to the rules eg not purchasing extra games feature before wagering complete, completed verification and sent in all required documents, you should be ok. If this was as a free no deposit bonus that you've claimed, there will most probably be a maximum withdrawal limit, probably $100/currency equivalent. If you haven't made a deposit and this was a free no deposit bonus and the last one was too, you'll probably be declined on the basis of claiming more than one no deposit bonus in a row "claiming consecutive bonuses". 

It might be subject to conditions such as a total amount to withdraw $5000 and a maximum withdrawal $20, which means you need to get over $5000, and when you withdraw, you only get $20 into your bank, and the leftover money gets forfeited after withdrawing your $20.

You can get best solution 9f your problem from your regarding casino that is Palace of Chance. Contact customer support and ask them to resolve your issue. 

All depends on the play through means what you have to pay the casino back for using there bonus 

Yes especially when you have a requirement on the max cash payout amout is $50 to $100 and once you withdrawl the excess amout disappears too leaving you with $0 balance so always read the terms and conditions for each bonus codes you redeem.

inclave casinos dont allow free bonus in a row and i had an experience similar even after playing from bonus balance to withdrawable and alot of bs if it cant pay shouldnt appear that way waste of time