Black screens happen when Obsidian is unable to load, the issue may be:
- themes
- plugins
- Obsidians preferences
- issues with your operating system
Zip or move your vault to another location so that Obsidian is forced to create a new vault. The location where you store your vault must be empty. If this works, don’t add any 3rd party plugins to the mix
Otherwise, go to your phone’s preferences and search for Obsidian, then delete its catches and preferences if possible.
If this doesn’t do anything, search for “reset iOs” in your browser to inform yourself how to clean phone preferences. I don’t have a iPhone but every device has some sort of save mode where you may be able to repair your phone to restore default preferences.
Attention
i don’t say reset to “default factory settings” because this would delete your phone data!
But in this save mode you should be able to repair phone preferences and what else. Finally, have a try and good luck!