Default user credentials depend on how the downgrade was done, with Web UI or with Flashwriter.
You can try the leftover option: admin/default
Please see details below:
DEFAULT USER ACCOUNTS
Previous firmware releases for the WR11, WR21, WR31, and WR44 devices included a default user
account with the credentials username/password. With firmware release 22.214.171.124, new routers will
no longer include the default username/password account. Instead, routers manufactured with
firmware release 126.96.36.199 will now have a default admin account and a pre-programmed unique
password that is displayed on the device label.
Special consideration must be given when upgrading or downgrading devices that cross this
functional boundary. The following special cases apply:
1. Upgrading routers that were manufactured prior to 188.8.131.52 (for example, 184.108.40.206):
a. If you upgrade the firmware to 220.127.116.11 using the Web UI Update Firmware1
, the router
retains the existing default user accounts. For example, after the upgrade, the router
will have a default username/password account running 18.104.22.168.
b. If you upgrade the firmware to 22.214.171.124 using Flashwriter, the default account will be
admin and the password will be default.
2. Downgrading routers originally manufactured with 126.96.36.199, that include an admin account with
a pre-programmed unique password:
a. If your router is running 188.8.131.52 and has the admin account with a pre-programmed
unique password, and you use the Web UI Update Firmware to downgrade to a release
prior to 184.108.40.206, the downgraded router will no longer recognize the pre-programmed
unique admin account password. Instead, the admin account password will be default.
b. If your router is running 220.127.116.11 and has the admin account with a pre-programmed
unique password, and you use Flashwriter to downgrade to a release prior to 18.104.22.168,
the admin account will no longer be present. Instead, the default account will be
i. After downgrading with Flashwriter, if you then upgrade to 22.214.171.124 or greater
using the Web UI Update Firmware, the router will retain the
username/password account and not include an admin account.
1. If you then factory default the router, the admin account with the preprogrammed unique password will return.
ii. After downgrading with Flashwriter and losing the admin account, if you then
upgrade to 126.96.36.199 or greater using Flashwriter, the admin account with the preprogrammed unique password will again be present and the
username/password account will be removed.