[SOLVED]
Attempted to connect to my laptop today, and to my surprise – connected successfully. To my recollection, I have not made any changes to background or connectivity protocol. I find this behavior totally bizarre. In any event file transfers from HDD back to the laptop are complete.
I will note that my Windows password (including symbol) remains. So, my presupposition that the 'symbol' was causing an issue was incorrect. I regret that I have no additional insight to share regarding the initial issue. Thanks for your timely responses.

So can you login with any other SSH/SFTP client?
Note that I believe that via SSH/SFTP you need to login with the actual account password, not with the PIN. I'm not 100%sure, but I believe the PIN is for local (on device) login only. For remote login, you need to password.

Negative. Newly Windows-10 laptop (server) has been configured for SSH/SFTP communication.
Prior to reconfiguration of the laptop, laptop was configured (Windows-10) with no password. WinSCP failed to connect. I added a password (no symbols) and was able to connect as expected. Successfully downloaded user files using WinSCP. Following HDD wipe and reinstall of Windows-10, Windows-10 requires symbols in the password. In fact latest Windows-10 updates attempt to divert users from password toward a PIN. I managed to load an earlier version of Windows-10 (to avoid the PIN requirement) however, cannot seem to avoid the 'symbol' requirement.
WinSCP is working as expected for other systems on my network. The newly configured laptop is the only machine I am unable to connect.

Do I understand right that you were using WinSCP GUI to connect to SSH/SFTP server running on Windows 10 machine? That server/machine was reinstalled – and now you cannot login. If my understanding is correct, I'm sure your problem has nothing to do with any symbols in a password. It's rather that the server is not configured correctly to allow the login. Can you login with any other SFTP/SSH client?

Relatively new to WinSCP. Have used to transfer files to/from RPis and Linux (Media) system. Very good product. Very easy to use. Current project is reloading Windows-10 on a laptop. Prior to system 'wipe', WinSCP connected to the laptop and files were transferred to HDD. Following new install of Windows-10 WinSCP fails to connect. The current version of Windows-10 requires at least one 'symbol' in the password. The symbol (!) appears to be unrecognized when the password is typed. I have attempted to replace ! with %21, but this also results in "Access Denied". I'm not attempting anything elaborate, simply providing the laptop's password. Recommendations?