My support has expired. Can I get it back?

If the seller offers renewal on that item, yes, at a price they set.

Where the option appears

On the item page and next to the item in My licences, once your window has run out. If you do not see it, that seller has not enabled renewal on that item, and there is no way to buy it.

How the new period is worked out

Renewal extends from where your last one ended, not from the day you pay. If your support lapsed in March and you renew in June for six months, you are covered to the following September. You never pay twice for the same stretch of calendar, and there is no advantage to renewing the instant it expires.

Renewing before it lapses

You can, where the seller offers it, and it stacks onto the end of your current window rather than replacing it.

Is it worth it

Renew if you are about to do real work with the item: a launch, an upgrade of something live, or an integration you expect to have questions about. If the item has been running quietly for a year and you are not touching it, you probably do not need to, since updates keep coming either way.

If renewal is not offered and you are stuck

Ask in the comments on the item page. Sellers often answer a genuine bug report from an out of support buyer anyway, particularly if it turns out to affect everyone. If the item is broken in a way that means it never worked as described, that is a refund question, not a support one.