Hi,
You don't have default DBMS. See wamp(64)/mariadb_mysql.txt file
You have modified a my.ini file to uncomment the line ;skip-grant-tables
It seems that the wampmanager.ini file is "corrupted"!
To repair it, you need to use the
Wampmanager.ini repair tool
Repair tool for wampmanager.ini file if it is corrupted or missing. You can download at any time, but install this tool only if you need it, because it takes into account the current configuration of Wampserver. A wampmamanger.ini corrupted file is reflected mostly by errors like "[EparseError]" or "Could not execute run action" when launching Wampserver.
Install this tool then read carefully the information windows at the end of installation.
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Documentation Apache -
Documentation PHP -
Documentation MySQL -
Wampserver install files & addons