As with every update, some folks are experiencing trouble completing the update and/or launching the game afterwards. I'll try to provide some generic troubleshooting:
There are essentially two places where updates occur. The "client" (the program/game itself) and the "assets" (all the fonts, graphics, sounds, text, etc). Either or both can experience corrupt data, particularly over poor connections, or when the servers are under heavy use (like right now).
So first the client, some signs the client update has failed:
G.Play or AppStore gives errors such as "failed to...", various "loop" errors, not enough free space, etc.
DS keeps saying there's an Update when you've already tried/done so.
What can be done about it?
Even if you didn't get a "free space" error, it's always a good idea to make sure you have alot of Storage space available. Over 1GB, or more is better. Even if an update can be downloaded, they're usually compressed. Extracting can suddenly require alot more space, and failure may not give a logical error. Freeing up space means deleting music, pics, or other apps. At least temporarily. Or shuffle things to an SD card if allowed.
If other apps are trying to update at the same time, pause DS and let the others finish first. Then recheck free storage or even reboot before continuing DS's update.
Clear the cache for the app store. IMO if there's a sign something got garbled it's best to just start fresh. Methods vary by o/s and version, some iOS even require something akin to a cheat code, ask for specific help below, or #your_favorite_search_engine. Other devices it's just a matter of locating your device's "App[lication] Manager". The app store will have its own entry, with an option to clear its cache.
If you are on mobile-data or other poor connection, chances of success are lower. If you have the option to wait for a decent/stable/unlimited wifi connection, that's recommended.
Next asset issue signs:
If DS says "Content update failed".
or DS hangs on the "Loading..." screen with a partial progress bar.
Once inside the game various buttons, text, or icons are missing, garbled, or the wrong thing.
What to do?
First make sure you've successfully updated the client if there is one. If some new asset is coded in such a way that only the newest client understands it, the old client will fail.
The servers could be overloaded. Try again later if possible.
When in doubt, clear the cache for Dragonsoul. For most devices this is the same, if not easier, than finding/clearing cache of the app store. There should be some sort of App Manager for your device, find the entry for DS and there should be an option to clear it's cache from there.
Or just keep trying. Particularly on weak connections, sometimes just trying again and again will fetch a little more each time. Tho corruption is a high risk this way, sometimes it's good enough to get in the door. Note the progress bar on the Loading screen and whether it gets further each time or if it "hit a wall". If it does go back to the above suggestions, this won't work.
Either of these issues can also be solved by completely uninstalling DS and reinstalling it. I don't recommend this unless there's a proven reason that's necessary. But some swear by it, so I mention it as an option. Be absolutely certain you have a good way to recover your acct(s) (usually Facebook) before starting this (which if you can't get in is too late). Also, ideally clear cache of the AppStore while DS is uninstalled.
any additional questions, ask below. I'll do my best, or try to get someone who can.