January 2020
Kept Getting this Error 51003 along with Error Stating that there was a problem Processing my Request when Trying to Purchase Star Wars Battlefront II: Celebration Edition
Tried clearing Cache in Firefox- Didn't Work
Tried to Order using Chrome Browser- Didn't Work
Both Browsers Multiple Times
Then Tried and was Successfully able to Order using Edge, There I saw that it Blocked Adobe Flash and the Order went through Successfully!
January 2020
Glad to hear that you found a workaround @Gandhi-Ji-1138.
I tested there and was able to make an order without issue, do you have extensions enabled on those browsers that could be causing the issue?
Darko