I just added a new cultivar
Begonia Lunar Lights™ Sterling Moon
but when i try to search DB it doesn't find it.
I am adding a multi-plant combo and cannot tag it.

hmm ... when I type Begonia Lunar Lights into the search bar it brings up both Sterling Moon and Dark Side of the Moon: https://garden.org/plants/sear...

something got fixed: it works for me now too. May be there was some delay with DB updates..

Yes, there is always a delay.
A tip is to find it in a separate tab/window (any plant you add is listed in your database contributions) and copy the plant ID number (the number is also found in the URL) and then paste that number in the plant combo search box.

That's a great tip! Thanks! Will do next time, if happens.