Can't log into 350-28 managed switch after firmware upgrade

[Norman54470]

I upgraded the firmware on my Cisco 350-28 Managed switch to the latest (2.5.9.54).  After it rebooted, I was no longer able to log into it with the credentials which formerly worked.  It is working fine, and everyone on my LAN has internet access, but I may want to make configuration changes in the future.  Could it have reset to default login credentials?  What are those?

[Kasun Bandara]

@Norman54470 hi, can you try to access device using console and check what is the configuration in the switch now. check if there was any resets happened during upgrade, if so IP address may be configured to default IP.

[Norman54470]

I guess I didn't describe the situation as clearly as I might have.  My router always assigns the switch the same LAN IP address, so I am able to access the login page.  But when I put in my username and password I get the error message, "Invalid username or password".  I have a record of every password I have ever used under this username, and none of them work.  I long ago deleted the default user, "cisco".  Even so, I tried the default username and password ("cisco", "cisco") without success. I have never used the console port; I probably mislaid the supplied console port cable years ago.  Even if I could connect to the console port, I would still, according to the manual, have to enter a username and password; and if they don't work in the web interface, they are unlikely to work in the serial interface either.  

I can think of another solution.  I could hold the reset button down for more than 10 seconds.  According to the manual this would reset it to factory defaults.  Presumably I would then be able to log in using the "cisco", "cisco" credentials.  I have a configuration file that I saved on January 28, 2021, and I could presumably load that file.  However that file contains my username, and an encrypted version of my password (as shown in the code below, with my username starred out).  How could I modify the file so that the default username and password are retained?

config-file-header
Cisco-Managed-Switch
v2.5.5.47 / RTESLA2.5.5_930_364_286
CLI v1.0
file SSD indicator plaintext
@
!
unit-type-control-start 
unit-type unit 1 network gi uplink none 
unit-type-control-end 
!
vlan database
vlan 2,1003 
exit
voice vlan oui-table add 0001e3 Siemens_AG_phone________
voice vlan oui-table add 00036b Cisco_phone_____________
voice vlan oui-table add 00096e Avaya___________________
voice vlan oui-table add 000fe2 H3C_Aolynk______________
voice vlan oui-table add 0060b9 Philips_and_NEC_AG_phone
voice vlan oui-table add 00d01e Pingtel_phone___________
voice vlan oui-table add 00e075 Polycom/Veritel_phone___
voice vlan oui-table add 00e0bb 3Com_phone______________
port-channel load-balance src-dst-mac-ip
no boot host auto-config 
no boot host auto-update 
bonjour interface range vlan 1
hostname Cisco-Managed-Switch
username ****** password encrypted 98f8cfd51539d7e483892879154b6ef33b20b278 privilege 15 
ip ssh server
ip http timeout-policy 0 https-only 
no ip http server
clock timezone Mt -7
clock summer-time web recurring usa 
!

[Kasun Bandara]

@Norman54470 ok. i suggest you to do a factory default reset and reconfigure switch. because i see only 2 VLANs in your backup unless you added more after this backup date. if you only configured VLANs, its easy to reconfigure. 

configure required settings like, time zone, VLANs and user names after reset.