Flight EI 120 was cancelled on Sat 14th as indicated by various monitoring agencies including Aer Lingus.
The flight replacing it on Sunday 15th was EI 1120 that was also cancelled.
This flight was replaced on Monday 16th by EI 2120.
Note three different flight numbers.
The EU directive EC 261/2004 is clear on how compensation is calculated.
In summary it is dependent on distance and it must be a flight by an EU airline when originating outside the EU.
If the flight is originating from an EU airport it applies to ALL airlines regardless of their home base.
The Aer Lingus flight originating in Orlando met all criteria for maximum compensation including route distance.
No expert but different flight numbers mean nothing as they are required for operational purposes. All EI have to do is show it was exceptional circumstances and by the sounds of the tech fault it they could just do that.
Do update if you do receive the full amount.