If you set the SD card as "Internal" storage and then changed it back to "External" storage, you may well have lost items that were on the card. Also, Chrome may be kind of 'stuck' due to the change. First try just restarting the phone and see if this resolves it.
Should that not work, then make sure that the SD card can be noticed by the device, and that you can access it through other apps. If you can, then next you need to clear out the Chrome app. So save or back up anything from it that you want to keep first. Since it won't notice the card, try saving to a cloud account or a computer (via USB cord connected to the phone).
Once you have saved what you want that is used with Chrome, go into the phone's "Settings", then "Apps". Go to "All" and locate Chrome. Tap it and then tap "Clear Cache" and then "Clear Data". Restart the phone and see if it works.
If it still isn't cooperating, then you may well have to uninstall Chrome completely, restart the phone and then redownload the app.