Dell switch S4048 -- Configure SNMP V3

this may help you:-

https://www.dell.com/support/manuals/en-us/dell-emc-os-9/s4048-on-9.14.2.4-config/setting-up-user-based-security-snmpv3?guid=guid-0afac628-3390-4cda-97d7-fc7325fd949a&lang=en-us

Hello, 

Could you try below steps please 

switch(config)# snmp-server user <username> auth <auth-protocol> <auth-password> priv <priv-protocol> <priv-password>
switch(config)# snmp-server group <group-name> v3 priv
switch(config)# snmp-server view <view-name> iso included
switch(config)# snmp-server context <context-name> v3 <group-name> read <view-name>
switch(config)# snmp-server host <host-ip> version 3 <username> <group-name> context <context-name>

Replace <username> with the desired username for SNMPv3, <auth-protocol> with the authentication protocol (e.g., MD5 or SHA), <auth-password> with the authentication password, <priv-protocol> with the privacy protocol (e.g., DES or AES), <priv-password> with the privacy password, <group-name> with the desired group name, <view-name> with the desired view name, <context-name> with the desired context name, and <host-ip> with the IP address of the SNMP manager.