In your regex you have to close the alternation using )
after:
(Message Picked from the queue....|Response Message :
Using a +
inside the character class would have a different meaning and would match a plus sign literally. The plus is greedy so you have to make it non greedy using a question mark to let [\S\s]+
not match all lines.
Update [\S+\s+]*>\n)
to
)([\S\s]+?>)\n
Your match is in the 4th capturing group.
(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}.\d{3})(.*)(Message Picked from the queue....|Response Message : )([\S\s]+?>)\n(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}.\d{3})
Regex demo
Not that if you don't need all the capturing groups, you can also omit them and take only the first capturing group (Demo)