The video can be flipped for various reasons, the main one is shooting with the camera in the initially wrong position. Other reasons may lie in the settings of your video playback program.
Check in which position on your computer another video opens with the same player. If it is played in the usual mode and the usual position, it is likely that this problem is exclusively for this video. For reliability, open it using another video player, if you have one on your computer.
After making sure that the problem lies precisely in the file parameters, download and install a special program for processing video recordings on your computer. Open the file you need and edit it by changing the position of the video in the encoding settings. After converting, check the results by opening the recording with a regular player that you use to watch the video.
If, nevertheless, the problem lies in the settings of the media player, it will not be superfluous to open the playback options and study the interface of this program. Find the setting you want and make the necessary changes. Also pay attention to the player's buttons on the toolbar, look for a special icon, perhaps you accidentally touched it from the main menu or pressed one of the hotkeys responsible for the position of the video in the player.
If you are viewing a video online, simply press the semicircular arrow button as many times as necessary to display the recording normally on the screen. In players on various resources, this button is located near the main playback control buttons.
One way or another, you can always find a solution to solve the problem with inverted video, even if it was originally filmed incorrectly. The principle of operation here is similar to changing the display of pictures on a computer - if you can change their position, you can perform this operation with video.