Paypal express session times out - unable to process credit cards

Until the earlier this week I was using Paypal standard which suddenly stopped working. Didn't process the 1st time, then sucessfully processed the second time I attempted but with that paypal screens looked different

Installed PayPal Express Checkout (rev1.5.3)

I get through to Paypal's site and enter my C.C info @ PayPal Guest Checkout. Fill out all my info and select don't create a don't want an account now. I do see most of the info prepopulated like address

On the Paypal Express Checkout I've filled in all my API info which I copy pasted directly out of Paypal

I'm now always getting "Your payment session has expired. To complete this transaction, you will need to enter your information again." Reinputting my information still gives the same error.

In all my searching here it sounds like its not really a timeout but that paypay isn't happy with my credentials or can't tie back to my account. I'm at a loss of what to look at next

Thoughts?

Just to try something else. I've deleted and recreated API credentials and enabled full logging

From PayPal Debug log - SetExpressCheckout

(live transaction) --> https://api-3t.paypal.com/nvp
Request Headers:
Array
(
[0] => Content-Type: text/namevalue
[1] => X-VPS-Timeout: 90
[2] => X-VPS-VIT-Client-Type: PHP/cURL
[3] => X-VPS-VIT-Integration-Product: PHP::Zen Cart(R) - PayPal/NVP
[4] => X-VPS-VIT-Integration-Version: 1.5.3
)

All the parameters look ok, not posting since there is some info that shouldn't be public

The response seems to indicate that the info is received, but still unable to not show a timeout error
Response:
Array
(
[TOKEN] => EC-5P131441HG5908847
[TIMESTAMP] => 2016-05-26T21:37:29Z
[CORRELATIONID] => fa51c5bc738f
[ACK] => Success
[VERSION] => 61.0
[BUILD] => 22457043
[CURL_ERRORS] =>
)

There was a known issue with older ZC versions that is corrected in ZC 1.5.5: https://www.zen-cart.com/showthread.php?215694-Known-Bugs-%28and-fixes%29-with-v1-5-4&p=1270902#post1270902