Timeout in ssms sql server 2014

1

I get the following message when running a complex query in SSMS
sql execution error
executed sql statement: SELECT list of table names...
error source: .Net SqlClient Data Provider
error message Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

I have increased the timeout period 600 secs on both the connection and query duration.

I am seeking some general assessments first.

2

The best option is to simplify the 'complex' query...the timeout is probably caused when SQL Server is trying to generate the execution plan and it finally gives up.

3

Actually, duplicate rows were on the input tables from SSIS. Once they were fixed the query ran w/o incident.