Please have a look at this Apple support article: http://support.apple.com/en-us/HT201377

If you buy the latest version in iTunes on your Mac or PC, you should be able to download the latest compatible version from the "Purchased" section in the App Store on your iPad.

It looks very similar to C. You could try to manually select the C syntax definition. Maybe it is better than nothing.

The latest version of Textastic (5.2) is updated for the higher resolution of the iPhone 6 and iPhone 6 Plus.

You can create a new file locally and then upload it to Dropbox using the file transfer screen (globe icon). 

For more info, have a look at this entry in the Trxtastic for iPhone manual: http://www.textasticapp.com/iphone/v5/manual/lessons/How_can_I_download_or_upload_files.html

Do you have a link with more information?

I plan to submit it to Apple this week. 

What exactly is the error message? 

Please try to enable the "Debug Log" setting in the connection's settings screen. Tap on the (i) button on the right side of a connection to change its settings. This creates a log file when you try to connect to the server which might help you find out what's wrong.

Yes, unfortunately this is a bug in the latest iPad version of Textastic. It will be fixed in the next update. Sorry for the inconvenience!