Why is PayPal forcing me to send money with a credit card ?

It only do that to me when I don't have money on PP account.

Maybe new policy adjustments by paypal? just did a quick look all i saw was this but doubt that will help you info Hope stuff will work out anyways :)

Does PayPal ask you to pay everything using your credit card or is it just for this particular trader or even this particular payment?

Because based on this information I see two possible answers to this issue:
Maybe there are restrictions to payment method if the account holder who you want to send money is located in specific countries?
Could it possibly be that you can somehow restrict which payment method somebody must be using if he wants to send you money?

Is there currency exchange involved? Because PayPal tends to think that you don't have enough amount of money on your account, even though you do but in a different currency than the one transaction is being held in.
Note: this happens (to me nearly every time) when you have funds on your PayPal account. Although there is a possibility it also works or rather doesn't like that with a bank account linked.

I don't think this really answers your question but I've generally found it easier with paypal to keep a balance for making payments to other people. I can understand why they'd prefer this rather than making lots of small debits from your bank all the time. It might be that they've changed policy to enforce that idea.

My thoughts are that the currency in your bank account matters. I assume your bank would use €. Also, it might be that the country you're sending money to (even if in the EU) is one you haven't sent to before and so you're encountering some policy about that country for the first time.

is the other user a personal or merchant account?

there was a time where steam required credit cards even when using paypal, otherwise most merchants (& sending/receiving to friends) have been fine (i have not tested with an unlinked card, the main issue is you want to fund from PP balance, right?)

edit: maybe it depends on not having money, it's not an instant transfer if it has to fund from your bank, so PP has to be the one taking the temporary loss & risk, maybe there is an option on the receiving end to make sure the money is real (aka having a PP balance or a CC)

I believe it's part of their new policy. If I remember correctly they are now charging some sort of fee that goes directly to the bank that gave you your credit card.... My guess would be that bankers got pissed because PP does not require fees so they are losing a lot of profit since people started using PP for free...

I think it's because it takes ~5 days for PayPal to receive money from your bank... judging by what happens when you try to make a transfer from your bank to PayPal. I never run into the particular problem you're describing because I keep funds on my account.

Personally, I don't think it's a huge risk to leave like $100 on your Paypal account. ~4 years ago, someone tried to make a transfer out of my Paypal account, but I support reversed it right away when I called them. The mobile authenticator helps a lot, too. :P

It could have more to do with the person you were sending it to. Unverified account or something could be the variable, but I'm uncertain. I sent money to a friend today and it used my bank just fine.