I'm in the same boat, (or should that be aircraft?)
Since January I had pre - 'requested' a row of three PE seats for my family, practically having a pick of the seats in PE when I booked.
On Monday, a notice of flight time change was on my booking to MCO next week. There was no time change but I had to tick the box to agree to it before I could further use my booking page. After I did that, the seat map disappeared and is now currently unavailable. I rang reservations to be told that there was no longer a row 25 on the A330 for my flight :0 .
(Slightly worrying that they can just remove a row of seats and wouldn't mind but I hadn't selected row 25

) ).
The guy on the phone told me the flight time was the same and so was the aircraft, so my question was, why am I getting no seats assigned when I had since January requested a row of 3 together? I was told I have a 2 together and then a single seat 2 rows away! v(
I understand and appreciate that seats are only requested.
I understand and appreciate that seats can be changed for operational reasons at any time.
What I can't understand or appreciate is being told a row of seats have been removed (?), they can't seat me altogether and hey ho, you will have to check in at the airport!
If they are to continue just moving you willy nilly, why offer the service of 'requesting' your seats? I'm not opposed to having to sit next to a total stranger for 9 1/2 hours (and I'm sure my mini monster would be quite happy not to have me around lol ), but to be honest I would rather not have to!