So been a OneWorld traveller for most of my life but looking to transfer miles to Emirates from credit card to redeem.

Thought I was pretty literate in all things flight/award etc. but I can't figure out what I'm doing wrong and any help would be appreciated:

1) I log in, click "Book Classic Rewards", one-way, Departing Date, ATH to EWR, First Class, and "My Dates Are Flexible'

2) I get message: "Sorry, no flights or fares are available for your selected dates. Please select alternative dates from the options below."

3) I then select a date which I assume is available since this one doesn't display "Not applicable" but instead "from 87,00 miles + EUR 136" with "Outbound ATH>EWR First Class" in the left hand column.

4) In the field below "Your current selection" it says "There are no First Class fares available for the dates you selected. We’ve provided Business Class fares instead."

5) Fair enough so I click "See Flights" but then I guess "Sorry, we were unable to find flight options to match your search. Please try a different search, or try your original search again later."

Am I doing something wrong or this is the trial/error method I need to go through to find award space? This is happening consistently to me.