Since I installed RoboHelp 2019 back in July, I've always had the following issue with snippets:
When trying to create a snippet, the snippet file is automatically named after either the project name or my Windows user name. In effect, it always becomes myname.htm.
When I try to save the project after creating a snippet, it doesn't seem to save. The snippet doesn't appear in the snippet list. The only method that seems to work is to create one in the snippet folder itself.
As it's a big part of single-sourcing, I absolutely need to get this sorted. It's not really viable to do it that way all the time.
There have been a couple of threads about problems with creating snippets but this is a bit different. Whilst it may not seem relevant, does your username have an dots in it? my.name for example.
If it does, that may be behind the problem and it will be fixed in the next update that is due quite soon.
New UI or Classic? Have you applied all the updates since RH2019 came out?