Some interfaces on devices are not getting names or speeds, while other interfaces on the same device are getting names.
SNMP Rediscover and Refresh both work, but the names of just some interfaces do not get names or speeds set automatically.
These interfaces will appear like "Interface X" where Xrepresents the ifIndex of a interface you know to have Netflow data.
If the interface has an ifType of that matches on of these values, it will be excluded from polling by default, 1,18,37,100,101,102,103,104,134.
These ifTypes are blocked by default to reduce the size of the NFA database and make SNMP polling more efficient, as they usually will not have Netflow data on them.
If you do an SNMP Walk of a device and check for OID .18.104.22.168.22.214.171.124.1.3 which represents the ifType, you can see what ifType is assigned to the ifindex in question.
To find the ifIndex you are looking for search for the OID above, with the ifIndex after it, like .126.96.36.199.188.8.131.52.1.3.X where X is the ifindex.
Note that if none of the interfaces on the device have names or speeds, it would more likely indicate there is an SNMP polling issue with the device.