I exported NAS.MIB from my QNAP NAS451 and imported it with MIB Importer V3.5.8 without any issue. here is the log :
Import successful! Report for C:\temp\NAS.mib: Sucessfully included files: 3 of 3 Sucessfully imported OIDs: 167 of 167 OIDs that were useful for PRTG: 167
Saved this as NAS451.oidlib into snmplibs subfolder I ran SNMP Tester 5.2.3 with the newly created oidlib and i got results, especially 220.127.116.11.4.1.24618.104.22.168.1.5.1 witch is free disk for Volume1.
PB is that i can't import the snmp library in PRTG with the above mentionned error. i have to do it manually with a custom probe and target 22.214.171.124.4.1.246126.96.36.199.1.5.1
NB : I use PRTG 188.8.131.523
any help would be appreciated. thanks