An event added no time

Start with your Dashboard: does the event show up in the recent activity?

It shows up, but nothing was added. That is the rate card, not the connection:

Its value is 0 in Time Settings.
Your timer is already at the max time set on the dashboard, or at its end date: it cannot go higher.
The remaining time has dropped below the threshold set in Set Timer: below it, events are recorded but add nothing.

It does not show up at all. That is the source of the event:

Is the platform linked in Connections?
For follows: if a warning asks you to reconnect with Twitch, follows are not being read yet.
For Ko-fi: the webhook URL must be pasted exactly as copied, with the www.

Two cases are deliberate. A re-sub that follows a subscription of the same tier within the hour is ignored, because Twitch sends both for the same person. And one donation reported by two services at once is only counted once.

Making up for a missing event

Go to Add Time. Quick add and the custom amount put back the time that was owed, and Set current time puts the timer on an exact value if you would rather fix everything in one go.

The overlay is stuck or blank in OBS

An overlay that has not moved for a while is almost always a page OBS kept in memory.

Right-click the source, then open its properties.
Click the button that refreshes the page cache, then confirm.

If the source stays blank, check that the link was pasted in full from Timer Widget. An overlay also stays blank when the timer has been deleted or disabled.

In the source properties, tick the option that refreshes the browser when the scene becomes active: it prevents most frozen displays after a connection drop.

The time shown differs from one place to another

The timer and the overlays resynchronise on their own within seconds. A gap that lasts usually comes from a source left open through a network drop: refresh its page in OBS, or reload your browser tab.

A one-second gap is normal: each display rounds in its own way.

The timer does not start on its own

The automatic start follows the beginning of your Twitch stream, under three conditions:

Auto start/stop with stream is ticked on your dashboard.
The timer start date, in Set Timer, is not in the future: a stream that goes live before that date triggers nothing.
Your Twitch account is properly linked; when in doubt, sign out and back in.

My starting time is not applied

Saving a starting time applies it right away as long as your subathon has not started. Once it is running, your starting duration is kept for later, but the timer keeps the time already earned: that is deliberate, otherwise one click would wipe everything.

To apply it now, use Reset timer, or New subathon if you also want your statistics and goals to start over.

I get signed out of the site

Since the latest update, your sign-in is kept for 30 days, even if you close your browser. If you are still signed out:

Your browser may be clearing cookies on exit, or you are browsing privately.
You may have revoked Marathon-Timer's authorisation from your Twitch account.

Either way, signing in with Twitch again puts everything back: nothing is lost, your timer and your settings live on your account.

One event too many

From your event list, you can delete a line: the time it had added is removed from the timer.

The time removed is recomputed with your current rate card. If you have changed your values since, fix the difference by hand from Add Time.

Still stuck

Describe what you did, what you expected and what happened, with the approximate time: that is what makes it possible to find the event in the logs. The contact and bug report links are just below.