Lapsed friendships are often easier to revive than people expect — the awkwardness of reaching out rarely matches the actual reception.
How to reach out
A short, warm message acknowledging the gap ("It's been too long — thinking of you and would love to catch up") works better than an elaborate explanation of why you fell out of touch.
Rebuilding gradually
Start with a phone call or a single coffee rather than assuming you'll immediately resume the old closeness — friendships often need to be rebuilt in a new form suited to your current lives.
If the first reach-out doesn't get a response, it's fine to try once more later — people's timing and circumstances vary.