This is page listing common troubles (new) people encounter on Roll20 that aren't too obvious or clearly mentioned on the relevant Roll20 Help Center or Community Wiki pages, and where to learn more about them. The page maintained by the community.

Character Sheets

How to create a character

Character can only be created inside a game by a Game Creator or someone promoted to a Game Master. To use a specific character sheet template, you need to have one assigned to the game. Adding Character Sheet covers how to do both.

If you have created a Character Sheet for someone and they don't see it, you have probably forgotten to change the "Seen By" and "Controlled by" settings for it.

Separate Window

A number of problems with the character sheet can come from having it in a separate window, which among things disables drag-n-drop from the compendium and the Charactermancer.
Restrictions when a sheet is in a separate window

5E

Over half of all games on Roll20 are D&D 5E, and basically everyone use the D&D5E by Roll20 character sheet. It has an extensive documentation page: D&D5E by Roll20.

It has a list of known issues: D&D5E by Roll20#Known Issues

Compendium

Your players don't see the compendium content you have, unless you have turned on Compendium Sharing.

Dynamic Lighting

Updated DL vs Legacy DL

The Updated Dynamic Lighting(UDL) is still in development, and have a list of known issues, and doesn't yet have every feature of the Legacy Dynamic Lighting(LDL) system.

Bugs related to it should be reported in the UDL Bug Report thread.

Many recommend to still use Legacy Dynamic Lighting in your games, instead of using UDL yet. That being said, UDL have better performance and works well if you don't use some of the Dim Lighting/Darkvision settings.

Players see only black

There are more than one possible reason why the players might not see anything:

1. They might not yet have tokens on the current map, which would grant them vision. If you have just changed the active map that the players see, this is likely whats going on. Drag-n-drop their tokens from the N Journal to the right place on the map.

2. (LDL) The player-controlled tokens might not have the "Have Vision" checkbox selected. Open the Token's settings, check the box, and save it.

3. The map might have no light-sources, and the characters don't see in the dark. If you don't have "Global Illumination" turned on, the map is dark by default, and only light sources and dark-vision enables sight on the map.

Tokens

Linking Tokens

Linking Tokens to Character Sheets isn't all to intuitive, but there is a guide for it: Linking Tokens to Journals. If tokens aren't linked to a character sheet, they don't share stats, nor can you quickly drag-n-drop tokens to the map from the N Journal.

Tutorial

The tutorial have several know bugs, such as the P Art Library and u Jukebox sections not working correctly.

The general community advice is to instead create a real game to test Roll20's features in, and to see many of the Youtube tutorials available. Roll20 Crash Course and Keith Curtis' Starting from Scratch are two recommendations.

If you use the tutorial, only use it for the things that work, and when encountering any problems, assume it's a bug( and not user error) and skip the section and go to the next part.

Players

Players in a game have a much more limited number of things they can do on Roll20 than a Game Master(GM)/Game's Creator.

Here is a list of things players can't do in a game, which many new users or GM's thinks players can do.

1. Players can't create their own character sheet, or handouts. The GM must create and assign control of the character/handout to the player(s) for the player to be able to use it. (There exists an API called "Welcome Package" that can automatically do this for players when they join.)

2. Players can't update the image of the Avatar or the Default Token for their Character. Only the GM can do this.

3. Players can't import from their Character Vault unless the GM have enabled this setting.