Why does this show nil when I use string.match?

I am trying to get the letters/numbers at the end of a string after a ':' (ex: test:56, I would want 56). I tried using string match but it just shows as nil.

local RepStore = game:GetService("ReplicatedStorage")
local vote = RepStore:WaitForChild("Remotes"):WaitForChild("Vote")
local votes = game:GetService("ServerStorage"):WaitForChild("Votes")

vote.OnServerEvent:Connect(function(_p, v, pv, pvn, n)
    assert(type(v) == "number", "v must be a number")
    assert(type(pv) == "number", "pv must be a number")

    if pv == 0 then
        votes[v].Value = n.."_1" 
    else
        print(string.match(votes[pv].Value, ":(.*)")) -- Output: nil
        votes[pv].Value = pvn.."_"..string.match(votes[pv].Value, ":(.*)") - 1
        votes[v].Value = n.."_"..string.match(votes[v].Value, ":(.*)") + 1 
    end
end)