This warning is normal and usually issued in these circumstances, the first being the most common cause:

1. After DEVONthink has terminated abnormally, e.g., by crash or force quit.
2. When trying to access a database already opened by another person. This includes a database open in another logged in account on the Mac. DEVONthink is ​not ​made for multi-user simultaneous access.
3. If you were trying to open multiple copies of the same database. This is usually caused by copying and renaming a .dtBase2 file in the Finder, and should not be done.

Press Continue . DEVONthink will do a checkup to ensure the database is healthy and report if there are problems.

Be aware, there is no 100% bullet-proof clipping solution in any application. Dynamic variables, like network quality, reachability and responsiveness of remote servers, bandwidth throttling, etc., can effect whether content can be successfully clipped. When the clipping mechanism encounters an unresolvable issue, a bookmark is clipped so there’s at least something useful captured. Trying the capture again may produce the desired result.

If you feel sync isn’t working correctly, these are the first things to check:

• In DEVONthink on the Mac, see what is reported in Window > Log. Then check the Troubleshooting > Sync Issues section of the built-in help.
• In DEVONthink To Go see if there is a triangle on the sync icon in the bottom toolbar of the database screen. If so, tap it to see what is reported. Then check the ? > Help > Sync > Troubleshooting section of the built-in help.

If you need further assistance than you can glean from the help or the downloadable manual, you will at least have some information to pass along to the support team.