I'm playing on PC and i have this issue. Only i have problems with just about every milestone-completions. There are a few i have been able to pick up. but this just became an issue two days ago. Before i didnt have problems with this.
It started togheter with another issue where all changes i have ever made inside the game were reseted. Star card selections, weapon selection, emotes, victory poses for all classes both trooper and starfighters including all heroes. Also all of the changes made to video, sound, gameplay and controls were reseted.
For me there is no pattern what rewards i am unable to claim. Every category has issues with reward claiming. Also having issues where the daily loot-crate isnt possible to claim even though it says there is a new daily loot crate to pick up.
I have tried repairing the game and searching for new updates. I have looked for a solution but there is non as far as i can tell. I really hope that this is something the devs in EA are aware of and are looking for a fix to. So far i have about 10 rewards i am unable to claim and it rising in count by the day since im working on the multiplayer milestone completion. (btw 500 crystals and choker emote is a scrawny reward for all that work, just saying)
Anyway loving your game in every other aspect and having a blast playing!! :D