Acceptance is the act of accepting or receiving.
Acceptation is another word for acceptance, especially with the connotation of the object being well-received, or being approved of by the recipient. Acceptation also has a linguistic meaning of the generally understood definition of a word. This word is rarely used (outside of the French language) and even more rare to find it in its linguistic definition. Your safe bet is to stick with acceptance.
Side note: Sometimes acceptation is confused with exception, which describes something as being left out of the group or does not adhere to a general rule.
Lastly, acception was a valid word in the past, but it has now become obsolete.