I am having this same issue. For me it's frustrating because I got my last kill for my anniversary completion.
Product: Apex Legends
Platform: Origin
Platform Model: PC
AMD or Nvidia Model Number: AMD Ryzen 7 4800H with Radeon Graphics
Ram Size: 8 GB
Gametag/EA Account Name: ag918w35
Squad Mates: Zippy121 and Lobo6Gecko
Overlay Software: No
Which Legend were you playing: Mirage
Which Legends were your squad mates playing: Octane and Revenant
Where did this issue occur: Second Chance Trios
What part of the map were you in: The game ended in Hydroponics on Olympus
What were you doing when the issue occurred: Finishing a game in first place
Did your squad mates also experience this issue: Do not know
Match Number: First game of the day
When did this happen: 13/04/2021 04:44 pm EST
How often does this bug occur: First time
How severe is the issue: Unable to gain experience or wins; also unable to get final win for Time to Win and Stay Alive, which would have then awarded the Legendary Anniversary badge (the anniversary recognition is more important to me than the experience)
What Happened: I finished a Second Chance Trios game and our team was in first place. The "You Are The Apex Champions" screen played, and the kda number was correct. However, I gained no experience, the match time on the recap screen was 00:00, and I did not get recognized for either of my remaining anniversary challenges.