What's the most important skill in virtual selling?

Focus, and active listening.   Ideally, anytime you can physically be with a customer or partner is going to be more impactful for a high stakes purchase.  Especially at critical decision points.  Think about the customer experience, and your investment in them.  If the team you are selling to is not remote, being able to sit with them, chat 1 to 1, be in their environment is a competitive move.

Clear and Concise Messaging: Convey your message clearly and succinctly to avoid misunderstandings and keep the other party's attention.

Position: Make sure you are in the centre of the screen to command the space.

Eyes: Spend 80% of your time looking directly into the camera during the conversation.

Consider needs: LOQ-on. Listen, Observe, Question to understand and respond to needs and concerns.

Empathy: Build a connection by showing genuine interest and understanding of their situation, needs and wants.

Technical Proficiency: Be comfortable with the tools and platforms used for virtual selling to ensure smooth and professional interactions.

Adaptable: Be ready to adjust your approach based on the feedback and behaviour of the counterparty during the interaction.

Ears, eyes and smiles in equal measure.  Eye contact has to be natural, you would never steer at someone in person so relaxed eyes focused on the camera particularly when people are talking.  Equally, active listening, and questioning for clarity.  You do not need to have a cheesy smile but most resting faces look angry so a soft smile makes you look more attentive and happy to be in the discussion.

This is a good one and I have never really thought about it.  I think the skills are the same in person or virtual and there a ton of important ones but if I have to pick one as the most important I would say  "active eye contact" to be the most important skill.  It's much easier I think to get distracted when doing virtual calls and easier to know when you are not engaged.  This is equally important while in person but that's my take.   

Adding to all the great comments, here is one from "the left field", from experience. It seems that introverts function a lot better in a virtual sales space than extroverts. The latter are personalities who need to be with clients in real life, visit them, have lunches and dinners together, pretty much everything what worked in the "before virtual" sales world. 

Introverts are very focused, listen intently, take notes and ask goal oriented questions based on what they hear -  and those with sales talent know how to drive a conversation in short time to an actionable outcome.