A WhatsApp group link not working usually means an admin reset it, the group is full, or the group wants approval before you get in. It almost never means the link timed out.
You will see the claim that WhatsApp invite links expire after 72 hours. They do not. An invite link has no timer on it. It stops working because something changed in the group, and the list below is what that something usually is.
WhatsApp group link not working: the causes, most likely first
WhatsApp publishes no breakdown of why links fail, so this order is our judgement and not a measured count. Start at the top and stop when one fits.
The 72-hour claim, and why it keeps spreading
We could not trace it to any page WhatsApp has published. Our guess is that it gets mixed up with disappearing messages, which really do run on timers, and then repeated until it sounds like a rule.
The practical damage is real. People assume a dead link has simply aged out, give up, and never ask the admin for a new one. If a link has stopped working, the useful question is who reset it, not how old it is.
Telling the causes apart in a minute
Open the link in a normal browser first. If you reach a page with the group name and a Join button, the link is fine and the trouble is on your phone or in the group.
If you reach an error page, or the page names no group at all, the link is dead: reset, deleted, or damaged in copying. Compare it character by character with the original.
If you tap Join and get a request screen, that is approval. If you tap Join and are told the group is full, you know the cap was reached.
Still stuck? Find another route to the same group, such as a friend inside who can forward a current link. The steps for the part after that are in our guide to joining with a link, and WhatsApp's help centre has the official wording.
What does not break a link
Time does not break it, as covered above. Neither does the admin being offline, since the link is generated once and WhatsApp handles the rest. Having the admin saved in your contacts does not matter either.
A slow phone is rarely the cause. If the Join button appears, your phone has done its part, and what happens next depends on the group.
Asking for a fresh link without being ignored
Message the person who posted the link, or the group's admin if you know them. Say which link you tried and what the screen showed: reset, full, or a request that never got accepted. Admins answer specific messages faster than a bare "link not working".
Be aware that any directory, ours included, is a snapshot of links that admins can reset the next minute. A listing can be accurate when it is added and stale a month later without anyone doing anything wrong.
If you are the admin
Resetting the link is a useful tool, and it is also the commonest reason your own members complain. Reset it when spam arrives or when the link has been shared somewhere you did not intend. Then replace the old link everywhere you posted it, because every copy of the old one is now dead.
Turn on approval if you would rather vet people than reset the link repeatedly. It costs you a few taps per newcomer and saves the rest of the group from strangers.
If you only do one thing
Ask for a fresh link. It fixes most of the list above in one message. And if you are hunting for groups that are still accepting people, the WhatsApp group links directory is where to start, and our overview of how group links work explains how the pieces fit.