Plugin works like a charm in front-end, but I doesn't seem to work for administrator login as of now.
Am I doing something wrong or is the functionality site-only?

By default, when logging into a website using Joomla source code, you need to enter your Username and Password. However, in some cases, you'll want users to be able to use Email instead of their Username to log in. The plugin below will help you.
After activating the plug-in, users can log in to the website with their registered email account and password without worrying about forgetting their username.
This plugin works with Joomla 4,5 and 6.
After installing it, you go to the Admin page > System > Plugins > System - JMP Email Login > Enable it.
From now on, users can use both their username and email address to log in.
Note: There are some cases that after activating the plugin, the website may crash. When it does you can solve it by using your hosting's File browser to access the directory: plugins/system. Then change the folder name "email" to "email_tmp". Next, report your error to me, I will check and fix it.
I have been googling how to change the menu colours, as the black text on my purple background is not very readable. However everything I have tried to change the text colour of the Off-Canvas main menu text to white did not work.
Would you know what custom CSS I would need to change all menu items to white text (including submenus).
Probably need background colour to not be white when hovering over submenus
Any help you can provide would be gratefully appreciated (or a pointer to some useful help).
Thank you
see
https://siteupdate.vedicmaths.org/index.php
InPre-Update Check for Joomla 5.4.4
for Off-Canvas it says
Joomla cannot detect the extension's compatibility with the target version of Joomla.
have you implemented the compatibility stuff for Joomla to upgrade extensions correctly ?
Have got two off canvas menus working (1. for tools and 2. for main menu)
However I can only get the Main menu to display the first level of menu items.
Have you any suggestions for getting the sub menu items to display ?
N.B. the menu item with sub menu items does display a down arrow, but trying to click on it only display the item at the main menu level.
see
https://siteupdate.vedicmaths.org/index.php
If you want to see where I have currently got to