Just a data point for you all.

Could be an anomaly, but I applied for the e-visa online, payment successful, but never received my e-visa via email. E-mailed the contact given on the website, but never received a response. Finally went to Siem Reap and explained the situation at the airport. They told me to pay for the VOA and to take it up with my bank regarding the fee that was already processed. I called Chase bank and they allowed me to waive the payment, but it was still a hassle. Spoke to my tuk tuk driver about the situation and he said that he has seen this happen often.

Obviously, this could just be an isolated case. My e-visa from years prior worked out fine and two other e-visas in my party worked fine. So just FYI.