PayPal Express Not Working (change from PPL Std)

I recently upgraded my ZC to 1.5.7c and all seemed to be working, except....

I have been using PayPal Standard for years. When testing payments, all works well with COD or with a gift card!
When paying through PayPal, TWO Orders are generated, although there is only ONE Charge!

I did have a couple of orders the other day, and Did Not have duplicates (was still on PayPal Standard) :unsure:
I had (3) orders in a row today, and all-3 were duplicated.....

I thought that it was a sign that it was time to upgrade to PayPal Express.....

BUT !!

I installed PayPal express and I'm sure that my API Credentials are correct, but when testing and I click on the "Go to Checkout" button from the shopping cart page, I get a Blank-White Page which reads "Page Isn't Working" and ERR_TOO_MANY_REDIRECTS......

I really hope someone can help!!??

Please Help!!!

Since I tried converting to PayPal Express I have not been able to get to the checkout_payment page from the shopping cart.....

I have since

* Removed and reinstalled the paypal module
* Deleted and re-created the API Credentials then re-installed the PPL Express module
* Finally deleted all PayPal modules leaving only COD enabled.....

I still cannot pass the shopping cart page to start the checkout!!

I get the same "Page Isn't Working" & ERR_TOO_MANY_REDIRECTS !!!

PLEASE HELP!! Even with the PPL mods uninstalled I CANNOT Checkout...

redirects can be in both your cpanel (or equivalent) or a .htaccess file in your root. Your host should be able to help you with that.

What other plugins are installed to the site?
What other changes have been made as the recent post indicates that no matter the payment module, checkout can not occur.
What mydebug logs are generated in the logs folder? There may be information related to the issue in there, though there may not also...

Hi and thanks for the replies everyone..... Sorry for the delay in getting back to this!

My original issue here seems to be fixed.... Sort of!

Something happened during the change from Paypal STD to Paypal Express. The "test" account that I was using STILL cannot pass the shopping cart page, and still gets the white-screen error!

I do have Paypal Express working well now! I don't understand what happened to that individual test account?

Thanks again for the replies......