You can use these invite links.
They do not expire and can be used infinitely:

• https://discord.com/invite/SwpQUFWreW
• https://discord.com/invite/ZQdqSMSbBN
• https://discord.com/invite/exxxDPmQmw
• https://discord.gg/dhC6H5BPJm

If the link appears invalid for you, the issue is on your side, not the invite or the server.

All the links (and newly created invite links) are working correctly on my side.
If the lnks doesn't work for you, this means the issue is most likely related to your account or device, not the server invite itself. 

🛠️ Please make sure your account meets the following requirements:

• Email must be verified — Discord may block invites if your account email is not verified.
• Phone verification is required — The MDRG Discord server requires a verified phone number before you can send messages.
• Your account must be 18+ — The MDRG Discord server is an 18+ server. Accounts registered as minors cannot join and may be automatically blocked.

Other possible reasons why the invite may appear invalid:

• Regional restrictions — Some countries or ISPs block Discord features or NSFW content, which can cause invite links to appear invalid.
• iOS device restrictions — Apple devices sometimes restrict access to NSFW or 18+ servers.
• Previous ban — If your account was previously banned from the MDRG Discord server, invite links will always appear invalid.

Please note that only the MDRG Discord moderation team can handle unban requests or appeals.
Moderators on the Itch.io page cannot appeal MDRG Discord bans.