Nextcloud CalDAV connection problems

If 2Do cannot connect to Nextcloud, check the account details and the error returned by the server. These checks apply to both hosted Nextcloud accounts and servers you manage yourself. For the connection fields on your device, see the CalDAV guide for iPhone and iPad, Mac, or Android.

Check the address and password

1. Use an up-to-date version of 2Do and your provider's current CalDAV address. A typical Nextcloud endpoint is https://cloud.example.com/remote.php/dav/. If Nextcloud is installed in a subfolder, its address must include that subfolder. Use the provider's documented address rather than a normal web sign-in page.
2. Confirm your Nextcloud username and password for 2Do. If your account uses two-factor authentication, create an app password for 2Do; your normal web sign-in password will not work. Nextcloud explains how to create one in Manage connected browsers and devices.

429 Too Many Requests

HTTP 429 means the server is limiting requests. Nextcloud can return it when its login protection blocks a client IP address, so the error alone does not establish that 2Do is syncing too often.

Pause repeated manual sign-in or sync attempts and check the account details above. Ask the server administrator to check Nextcloud's logs for failed logins, throttled addresses, or blocked addresses at the time of the error.

If Nextcloud sits behind a reverse proxy, the administrator should check trusted_proxies and forwarded_for_headers. Nextcloud needs the real client IP address. If every connection appears to come from the proxy, one client's failed logins can cause other clients to be throttled too. Keep login protection enabled and correct the underlying cause. See Nextcloud's brute-force protection guidance.

After correcting the cause, allow the server's block to expire or ask the administrator to clear the affected block, then try syncing again.

Redirects and 405 Method Not Allowed

CalDAV discovery may redirect /.well-known/caldav to the account's DAV service. A 405 response can mean the request reached an ordinary web page instead. Check the address and app version before assuming the server is misconfigured.

For a server behind a reverse proxy, ask the administrator to make sure:

• /.well-known/caldav leads to the Nextcloud DAV endpoint, usually /remote.php/dav/, including any installation subfolder.
• The redirect keeps the intended HTTPS hostname and port. It should not send the client to an internal server IP address, an HTTP address, or a web sign-in page.
• Nextcloud receives the correct hostname and protocol from the proxy. Its overwritehost and overwriteprotocol settings can correct detection when needed.

On iPhone, iPad, and Mac, 2Do blocks redirects that would forward an authenticated CalDAV request body to a different server address or downgrade an HTTPS connection to HTTP. Correct the server's redirect rather than entering an unfamiliar destination in 2Do. See Nextcloud's reverse-proxy configuration guide.

If the connection still fails

Send 2Do support the exact error, your app version, and a diagnostic report from 2Do's settings. Include the date, time, and time zone of one failed attempt. If you manage the server, include the matching Nextcloud and reverse-proxy log entries, with passwords and authentication headers removed. Matching the two sets of logs helps distinguish server configuration from an app compatibility problem.