To resolve the issue of not being able to delete messages in Canary Mail on iOS while it works fine on your Mac Desktop, you can follow these steps:

Check Delay Archive/Delete Setting

1. Open the Canary Mail app on your iOS device.
2. Navigate to the app's settings.
3. Look for the Delay Archive/Delete option.
4. Modify the setting to a shorter time or disable it completely if it is currently set to 5 or 10 seconds. This setting may be causing the app to delay deletion actions - learn more.

Verify Mailbox Settings

1. Go to Settings on your iPhone.
2. Scroll down and tap Mail.
3. Select the email account you're having trouble with.
4. Tap on Account, then go to Advanced settings.
5. Make sure that the Deleted Mailbox is set correctly—ensure it’s pointed to the folder where deleted emails should go. Sometimes improper settings can restrict deletions - learn more.

Check Internet Connection

1. Ensure your iOS device is connected to the internet via Wi-Fi or cellular data.
2. Try toggling the connection off and back on to refresh it, as connectivity issues can sometimes lead to sync problems - learn more.

Reboot the App

1. Close the Canary Mail app completely.
2. Double-click the Home button (or swipe up from the bottom of the screen on newer iPhones) to see all apps in use.
3. Swipe up on the Canary Mail app to close it.
4. Reopen the app and try deleting your emails again.

Reboot Your Device

1. If the above steps did not work, consider restarting your iPhone.
2. Press and hold the power button until you see the slide to power off option.
3. Slide to power off, wait a few seconds, then turn the device back on.
4. Once back on, try the deletion process again.

Revoke and Reconnect the Account

1. In the iOS Mail settings, find your email account again.
2. Tap Delete Account to remove it.
3. Restart your iPhone.
4. Go back to Settings > Mail > Accounts and select Add Account to re-add your email account.
5. After setting it up, test deleting emails in the Canary Mail app once more - learn more.

If none of these steps work, consider updating the Canary Mail app to the latest version or contacting support for further assistance.