Alternate my flex rows

.services-flex will always be an only-child in each dyn-item, which is an odd number, so your CSS rule doesn’t apply to it.

You should nth-child the dyn-item instead:

.service-flex-master .w-dyn-item:nth-child(even) .services-flex {
    -webkit-flex-direction: row-reverse;
    -ms-flex-direction: row-reverse;
    flex-direction: row-reverse;
}

See how fast you can receive an answer if you post the required information?