Reinstalled whatsapp and cant access group chats.

When you reinstall the app, you get an option to load those previous messages. In this case, you would have your app as it was before you uninstalled.

I'd also recommend to reinstall again and activate the backup-function as Vikas stated. You should automatically join the groups, even if you didn't use the backup. Did you verify your phonenumber already??

Yes... Agree with @Igel Chris to re-install it again...

And yeah you should have selected the option to store the back up conversations.

Even if you click restore, actually the restore data is very small. So you still can't get the messages and groups you once belonged to

I am having the same problem. Please help me if you got solution

After reinstalling whatsapp I've lost all my group memberships and am not getting new messages.
Why???
Is there any urgent method to contact whatsapp?
I've lost membership in a group where I was the only admin. So how to get it back?

If the above steps don't work, try clearing the cache of the WhatsApp application. On Android, go to "Settings" > "Apps" > "WhatsApp" > "Storage" > "Clear Cache." On iOS, go to "Settings" > "General" > "iPhone Storage" > select WhatsApp > "Offload App." Afterward, reinstall WhatsApp from the App Store or Google Play Store.

Losing WhatsApp messages and group chats can be frustrating, but there are a few steps you can try to recover them. Here's what you can do:
Confirm with other members of the group chats if you are still listed as a member. If they can see you in the group, it means you are still part of it.
Make sure you have the most recent version of WhatsApp installed on your device. Updating the app may resolve any issues related to receiving messages.
Verify that your notification settings for WhatsApp are properly configured. Go to your device's settings, find the WhatsApp app, and ensure that notifications are enabled.
Request a member of the group to add you back to the group chats. Once you are added back, you should start receiving messages again.
Clearing the cache and data of the WhatsApp app may help resolve any issues related to receiving messages. Go to your device's settings, find the WhatsApp app, and clear the cache and data.
If none of the above steps work, you can try reinstalling WhatsApp. Before doing so, make sure you have a backup of your important chats and media files. After reinstalling, verify your phone number and restore your chats from the backup if available.

If you've reinstalled WhatsApp without a backup and are missing group chats, try having someone from the group send you a direct invite link. If local data restore fails, unfortunately, you may not be able to recover the lost messages.