We can not help you here sorry.
Because this forum has nothing to do with any trading accounts (the trading accounts are related to the brokers only).
Besides, the demo accounts are provided by the brokers for limited time in most of cases.
read post #28 for more explanation.

How do I add a stock symbol to MT5? - How to open a demo account with Metatrader in your MT5 list
- 2020.10.12
- Sergey Golubev
- www.mql5.com
And read this thread as a practical example about how to add the broker to your mt5 list to open demo (or real) accounts. I remember some users on russian forum complained about this phone/email verification process (confirmation code) during the openning the demo account for many brokers (yes, some/many brokers will ask to verify phone/email for demo account), and it is new reality sorry
It's always better to download the custom branded MT5 terminal from each broker's website, install it and use it to login into the corresponding trading account of that broker.
Using the same MT5 terminal for all trading accounts from all your brokers may cause such issues.

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Hi traders!
Please help me solve issue with login to servers other then listed by default in MT5.
As you can see on screen my three first logins works fine but I created it in MT5.
Oanda and FusionMarkets Demo accounts were created outside MT5.
I can not log to them, I do it by right click on Accounts -> Login to Trade Account and then typing user and password and server. These accounts are valid and works outside MT5.
I tried on Mac and PC, neither worked.
What am I doing wrong? Please help