404 Error and wp-admin

I’ve lost perspective. Below are the two issues:
The requested URL /www.mywebsiteexample.ca/wp-admin/ was not found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Summary
1. Developed website locally and uploaded files to a subdirectory of the root.
2. The website in root file was new and only used for a Temp Home Page with index.php.
3. Moved out old root website and moved in newly uploaded WP site into root directory.
4. I enter url and am able to see the WP login box; then after entering uname and pswd get the above error message.
5. Have tried a couple options with .htaccess – without success.

My next plan was to deactivate all plugins then upload.
Am confused now. Uncertain of the correct sequence of steps.

Thanks in advance for your laser insight.