Oracle config files are pretty particular about formatting. It's a leftover from the 20+ years ago Oracle wrote the code.
Make the tnsname.ora entry look like (copy and paste exactly as-is):
onstaff =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = A606)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = onstaff)
)
)