Paypal says Please try again later


I tried the paypal using the sandbox and it worked ok. However,

When I try to process a buy paypal (I set up an item €1 e.g.) to test if the paypal works I got this message:
"Things don't appear to be working  at the moment. Please try again later."

I have used the correct pdt for Production .(I got other for my sandbox account)

Thanks in advance
BTW,  it works OK with the sandbox, the problem is when I change my PDT and go Production mode. 
I have no idea, there have been no such errors reported from the module.
If you search for other users with the same problem on Google. Do you get any clues?

I was researching and I found something in paypal but it does not apply to my problem. Anyway, I contact technical support paypal and opened a ticket today, after tried many diferents options such as create other subdomain, install lite cart again, paypal again, etc , but not luck ;-(

I will inform any update from them so.

If you think I could send any screenshot or whatever to have a look, just tell me.

Hi again,
I have the issue solved! It was a problem of my paypal business configuration.

Here I leave some clues just for somebody who gets stuck like me in that message. ;-) 

Answer by paypal:

"Dear Merchant,
Thank you for contacting Merchant Technical Services.
I have checked your code and it is working if I use my PayPal account.
So, I figure there must be a setting into your account which is blocking this procedure. Because your account is verified, it then must be that you have to enable your account to receive Non-Encrypted buttons.
So, if you go in here after you login, you would be able to modify this feature."
Please find the screenshot with the solution in the attachment
Wow, who could have guessed! Good job.