Error messages following integration step

Converting data through different engines is not the best approach indeed. APP reads various formats, but not png indeed, the best is to get them into their raw formats at the beginning and use those directly or first converted to dng if APP can't read it. However it shouldn't produce an error I think, are you using calibration data in this way as well (converted to tiff etc) ?

Thanks for replying Vincent.  (I only noticed they were png when I came to stack them, but DSS accepts png so I was able to use them at that time). I used a master dark which also had been converted from png to tiff using PS. There were no other calibration files. In future I will certainly aim to save captures directly to fits or tiff which APP reads natively. In the meantime is there a reliable way to convert png to another format APP will read? Do you think this the issue which prevents the Integration file from opening in APP?

Can you read the error message for me?

No, the error message has more to do with the Java programming. But as you said you used a converted calibration frame, this might trigger such errors sometimes. What happens if you leave out the calibration data?

Not sure if png has the entire and un-altered data in it to be honest, so not sure if that'll work. Certainly may have issues, not working at all, for calibration data. DNG is a format used when camera's that don't have native support, are supported in that way.

I've tried without the master dark frame, lights only, and am getting, I think, exactly the same error message.

Mmmmm, then I think it's the files themselves that are causing an issue. Could you upload maybe 5 for me to have a look at? If you can use wetransfer.com for that that would be great, my email is vincent@astropixelprocessor.com

Thanks Vincent. 5 files (in 2 emails) sent as requested.