No need to be sorry for asking, in fact, I apologize for not coming back to you earlier.
Unfortunately, I haven't been able to reproduce your issue. I've installed Mantis 2.21.0-1 on a fresh WIndows 10 machine and everything works for me:
Looking at your logs, the only strange thing that I found were the errors in the MySQL logs that @jota mentioned earlier:
2019-10-10T08:03:50.067912Z 0 [ERROR] InnoDB: Operating system error number 2 in a file operation.
2019-10-10T08:03:50.068980Z 0 [Note] InnoDB: Some operating system error numbers are described at http://dev.mysql.com/doc/refman/5.7/en/operating-system-error-codes.html
2019-10-10T08:03:50.070477Z 0 [ERROR] InnoDB: Cannot open datafile for read-only: '.\bitnami_mantis\mantis_api_token_table.ibd' OS error: 71
2019-10-10T08:03:50.071733Z 0 [ERROR] InnoDB: Operating system error number 203 in a file operation.
2019-10-10T08:03:50.072677Z 0 [Note] InnoDB: Some operating system error numbers are described at http://dev.mysql.com/doc/refman/5.7/en/operating-system-error-codes.html
2019-10-10T08:03:50.074155Z 0 [ERROR] InnoDB: Could not find a valid tablespace file for `bitnami_mantis/mantis_api_token_table`. Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting-datadict.html for how to resolve the issue.
2019-10-10T08:03:50.076260Z 0 [Warning] InnoDB: Ignoring tablespace `bitnami_mantis/mantis_api_token_table` because it could not be opened.
This link in the Oracle documentation says that the error is due to that file missing. The solution according to it is to run
DROP TABLE on the missing tables, but I believe that is going to break your Mantis installation even more. Can you list the files in your
C:\Bitnami\mantis-2.21.0-1\mysql\data\bitnami_mantis directory to see if there is something weird there?
There's this thread in the Mantis official forums in which an user describes the same issue as you. However, it seems to be solved by logging in once as admin, which is something you can't do.
Do you have any other Mantis installation in the machine? Can you do another installation to check if the issue is still happening?