How to test coupons?

[MgmtSpec]

Hello,

Having a LOT of trouble with coupon links. Wasted more than an hour "testing" coupons. My understanding is the coupon URL should ADD the item AND apply the coupon.
I did a one time use try - and that seemed to work. All subsequent test failed even AFTER editing coupon to NOT be one time. I've cleared browsing history, deleted and recreated multiple times. The lastest "Test" link

http://www.managementspecialties.com/cgi-bin/sc/order.cgi?storeid=*2e11a2e17ea0a3c6eb041f9a50420a177ef82649a70ca98445&rec=8&cpid=7d6daa92-8780-11e7-99db-0030488cbea5&function=add

Returns:
"TEST
Coupon Not Applied"

Because no product.

I'm hesitant to send coupons as they do not appear to work reliably. There must be something simple or basic I'm missing...

And NOT impressed with the coupon interface at checkout - using MobileTwoCart - which seems to be the only one that works somewhat decent by default on mobile.

Its not intuitive to enter coupon code and NOT have an "Apply" button nearby to confirm.

It seems the interface front and back end is getting worse with each update.

[MgmtSpec]

Here is the product link that is assigned to that coupon...
http://www.managementspecialties.com/cgi-bin/sc/order.cgi?storeid=*2e11a2e17ea0a3c6eb041f9a50420a177ef82649a70ca98445&dbname=products&sku=GMORPLUSMO&function=add

[loren_d_c]

"My understanding is the coupon URL should ADD the item AND apply the coupon."

Coupons and products are added to the cart separately.

-Loren