The merchant's account is not able to process transactions

[otrcomm]

Hello,
I have seen this issue referenced before here in the Community, but have never seen a solution.
I have just set up a sandbox account to try and test a wifi network I setup with Ubiquiti Unifi equipment. When I tell the Unifi Controller to process payments through the PayPal Sandbox I get an onscreen payment box error that says "Unable to process the payment" and in my Unifi server log I get:

[2018-02-15 06:48:52,121] <portals-15> ERROR guest - PaypaloDirectPayment() failed. url=https://api-3t.sandbox.paypal.com/nvp, result={ "ACK" : "Failure" , "AMT" : "5.99" , "BUILD" : "39206242" , "CORRELATIONID" : "da0700fe211f3" , "CURRENCYCODE" : "USD" , "L_ERRORCODE0" : "10548" , "L_LONGMESSAGE0" : "This transaction cannot be processed. The merchant's account is not able to process transactions." , "L_SEVERITYCODE0" : "Error" , "L_SHORTMESSAGE0" : "Invalid Configuration" , "TIMESTAMP" : "2018-02-15T13:48:51Z" , "VERSION" : "56.0"}

I was using these Sandbox account:
Username: <removed>

Any ideas?

Regards,
Murrah <removed>

[otrcomm]

That should have been:

...

...
[2018-02-15 06:48:52,121] <portals-15> ERROR guest - PaypaldoDirectPayment() failed. url=https://api-3t.sandbox.paypal.com/nvp, result={ "ACK" : "Failure" , "AMT" : "5.99" , "BUILD" : "39206242" , "CORRELATIONID" : "da0700fe211f3" , "CURRENCYCODE" : "USD" , "L_ERRORCODE0" : "10548" , "L_LONGMESSAGE0" : "This transaction cannot be processed. The merchant's account is not able to process transactions." , "L_SEVERITYCODE0" : 

...

...

I do not know how the smiley got in there.

[otrcomm]

No this did not correct the issue. Same error messages.