Version as of this post, with errors:

In the not so distant future, Theodore, a lonely writer purchases a newly developed operating system designed to meet the user's every needs. To Theodore's surprise, a romantic relationship develops between him and his operating system. This unconventional love story blends science fiction and romance in a sweet tale that explores the nature of love and the ways that technology isolates and connects us all.

The errors:

1. There should be a comma after "a lonely writer", which is an apposition and therefore requires being surrounded by commas.
2. "needs" should be "need", as in "meet the user's every need", since the word "every" must be followed by a singular noun or noun phrase.

Corrected version:

In the not so distant future, Theodore, a lonely writer, purchases a newly developed operating system designed to meet the user's every need. To Theodore's surprise, a romantic relationship develops between him and his operating system. This unconventional love story blends science fiction and romance in a sweet tale that explores the nature of love and the ways that technology isolates and connects us all.