@Apollon1001
When videos are finished processing, they usually disappear briefly - they are not visible in your list of videos, even if you're logged in. Then they reappear on your profile as "inactive" until they are checked by website staff to ensure that they are not illegal or a breach of the website's TOS.
If they completely disappeared and did not return to your profile, there is a chance that they were deleted because they were illegal or a breach of the website's TOS.
In some rare cases, videos that have errors will fail to process properly when they are processed again, these videos might also disappear permanently.
If your video was not illegal and did not violate the website's TOS, but disappeared for longer than a few days after processing, then try reuploading it.