DB2 Query Error SQL0204N Even With The Schema Defined
Maybe there is a problem with upper and lower case. I created a table using the following statement: 

CREATE TABLE "FOOBAR"."Users"  (col1 INTEGER)

If I try try to run on of the following statements at the CLP I get an error SQL -204

db2 "select * from db2root1.Users"

db2 "select * from db2root1.USERS"

db2 "select * from db2root1.users"

Always the error message  SQL0204N  "DB2ROOT1.USERS" is an undefined name.  SQLSTATE=42704 is returned. 

I would suggest to run the following statement and check the spelling of the table name. 

select t.tabname from syscat.tables t where lower(t.tabname) like 'user%'

Some tools are creating the tables with a case sensitive table name. This may result in an SQL -204 in some scenarios.  

In this case drop and recreate the table without any quotation marks.