No. Answers are not case sensitive— using uppercase, lowercase, or a mix won’t affect whether your Answer is considered correct. However, spelling still matters: typos, misspellings, and incomplete Answers will be marked incorrect. If your Answer is not clearly the correct term for the Mystery Item (in standard American English), it may be ruled wrong, and an incorrect Answer will knock you out of that Round’s Prize Pool.

Sections 3.4 and 3.5 of the User Terms & Conditions breaks down Judging an Answer, Spelling, and Typos.