Hi @Syed Harith Zaki,
I'm glad to hear you solve the problem ,if you have any issue about SharePoint, you are welcome to raise a ticket in this forum.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others." and according to the scenario introduced here: Answering your own questions on Microsoft Q&A, I would make a brief summary of this thread:
[How to resolve 'Selected user account does not exist in tenant and cannot access the application' error?]
Issue Symptom:
A guest user experiences the error stating 'Selected user account does not exist in tenant 'Microsoft Services' and cannot access the application in that tenant. The account needs to be added as an external user in the tenant first. Please use a different account.'
Solution:
You might use personal Microsoft Accounts (Outlook, Hotmail or OneDrive), you are connected to the Microsoft Services tenant by default. Within the default tenant, there is no linked directory for performing any actions might cause the issue. As a workaround, create a new user fixed the issue.
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!