There are two separate aspects to providing support to another.
First, you need to observe the behavior or acknowledge the circumstances. Has the person been under considerable stress? Do they seem in an uncharacteristically sour mood? Are there signs of the person being overwhelmed? Did a rough situation happen in their life?
Then, if you address the issue, you need to leave space for them to choose the response. Someone who has encountered tragedy at home may see their volunteer time as a welcome escape rather than an obligation. A person who has lost a loved one may prefer to be alone — or may be delighted by an invitation. Someone who is ill may wish to talk about their worries or may prefer to be distracted from them.
And the reverse may be true for them tomorrow.
It’s easy to see a gloomy behavior or hear about unfortunate circumstances and want to jump in with the best of intentions. But make your actions about them, rather than about you. State your observation but then ask what would be helpful rather than assuming you know. What constitutes support can only be determined by the recipient, not the giver.