There could be several reasons why it shows that message but first you should remove any prompt=no in your .cnf file , that way you will get a prompt if fields are missing.
The reasons that I can come up with are you misspelled something like the distinguished_name field, openssl will not complain about "unknown parameters" so if you misspell distinguished_name as distinguised_name for example, you will get the Error: No object specified in config file because you are not specifying any distinguished name.
For example the following server.cnf file will trigger that error:
[req]
prompt = no
distinguised_name = dn
input_password = xxxxx
[dn]
CN = xxx.myexample.com
emailAddress = [email protected]
O = MyExample
L = Stockholm
C = SE
Again the reason is the misspelled distinguised_name which should be distinguished_name.