Compatibility Issue - Apple IOS 8.3

I have no real information except to say that if you do a search of the forum, I recall reading a couple of other posts regarding this. You may have to wait for an update from Apple to fix this.

You can either roll back to 8.2 (you will have to use Google to do this and neither Apple nor Bad Elf recommend it but Apple has left the iPad version of 8.2 signed) or you can wait and you will be able to use it with 8.4.

Some have fixed the issue with firmware updates to their devices.

update to IOS 8.3 external GPS doesn't connect to iPad

Re: GPS data not available to apps after iOS 8.3 update

That won't work with Bad Elf, Firelight and other similar higher end GPS. The two links you provided had no luck whatsoever with the recommendation to upgrade the firmware on the Bluetooth device. Completely read the first one.

The posts that jazcan nicely provided for you won't give you a fix but if you read the second one it will give you more information about the issue. They are the threads Chris was referring to.

I tried yo downgrade since several weeks: It does not work. "your iPad is not eligible for 8.2" (iPad 2). Upgradind the firmware for DUAL 150 made it even worse: now my GPS / Fore Flight doest even work with my older iPhones 3S and 4 any more 😢

Back to sectional chart and pencil: The progress nowadays is really overwhelming. The FAA check pilot was absolutely right demanding navigation the "good 70 year old way" My demand for electronic gadgets in my plane is absolutely more than satisfied, specially from Apple, using them since 1983, experiencing over and over again a DOWNWARD INCOMPATABILITY.

You did download your .ipsw file from Apple?

I'm guessing the next release will be around WWDC keynote which would place it around June 8th if you can wait that long.