Where do I install the expansion card on Roland Juno stage

https://www.roland.com/uk/products/juno-ds/
https://www.sweetwater.com/store/detail/JunoDS61--roland-juno-ds61-61-key-synthesizer/reviews
https://www.sweetwater.com/store/detail/JunoDS61--roland-juno-ds61-61-key-synthesizer/reviews
https://www.rolandus.com/blog/tag/juno-di/
https://www.amazon.com/Roland-Lightweight-Weighted-action-Keyboard-JUNO-DS61/dp/B016NUAL5Y

The information is in the manual. You can download a copy here-
JUNO Owner Manual JUNO Manuals Support Roland

Roland Juno gi program error problem

Well it could be a sereis of things. First of all, check compatibility with your opperating system, if that is ok go back to the Korg website and re-download again.

It MAY require the flashcard to be left in... in other words they may NOT download and transfer the flash update card to internal memory.

Check if headphone output is normal... sometimes the headphone jack switch fails and doesn't send to speakers when headphones are unplugged.

Here is the link you need but pay absolute attention to the Please note section in each case as the Juno D LE and the original Juno D are different. If you install the wrong update you will have problems with the keyboard working at all.

you could try using 2 midi channels for two sounds.

juno, lovely instrument, try the synthesizer repair centre in london

Normally you have to clean the conductive rubber "pills" AND the circuit board traces they get pressed down on.

USE ONLY 99% isoprophyl alcohol on Q-Tips to do the cleaning and be gentle.

Use of other product like deoxit and other contact cleaners will wreck the contact material.