When using the pluging, the character disappears and only the shadow is visible, and the enemies are facing in the opposite direction even though they are oriented to the right.

Most likely an asset standard issue, unless you're referring to an error due to third party plugin conflicts. I will assume the former. 

• If you're still using the default 9 by 6 arranged SV battler sprites, they aren't gonna work. Either rearrange them in an image editing software to be 1 by X (X since you can have any number of frames for a motion), or have each animation frame in its own .png file. 
• Check that your actors have a <battlerId:identifier> tag in their respective notes section in the Database. 
• All graphics for SV battler sprites should also be left facing since the plugin allows for dynamic direction changes during an action sequence.  

Talk to this NPC in the demo to be guided by the asset standard for side view battler sprites.