A few things to try.

When it says "connection refused" it means the bitcoind program stopped running.  Back a few messages, I recommend a way to monitor your node in real time with live scrolling of the debug.log.  It's very important to monitor that log as it tells you how the download is going with the database.
Sometimes you can just restart the node and it will pick up where it left off.  If you click on the button multiple times trying to force restart it can crash bitcoind.   Sometimes just restarting the system can fix the issue and restart the bitcoind.  I've had it where the bitcoind crashes, won't restart with the node start button, but shutting down the system and restarting fixes it and the bitcoind restarts normally.  Especially after a chainstate database crash.

having a running log window open allows you to see the progress and see how it stopped.  Did it just crash or did it exit or close.  you can see that in the logs.

Having the miner running may stress the power supply and for some reason the cpu is sensitive to power spikes.    that can cause a crash.  open the system monitor so you can see how busy the cpu is when downloading the blocks.  It's not a simple download, it decrypts it which takes cpu power and sets up the database.    In system monitor you can also see if bitcoind is running or not and how much resources it is taking up.

I have my unit on backup power with line conditioners.  Also only running the IBD"Initial Blockchain Download" is best.  don't have multiple browsers open and really, don't mine until it's complete.  bitcoind will use a lot of memory when downloading.  

Once the download is complete I can tell you that the system runs pretty well.  In eco, normal, or turbo, depending on your temp and noise preference.

I had problems with my microsd card that i changed out and i got two of those and also 2 pcie cards.  Once the IBD is complete I made a backup of the blockchain on the second pcie in case i had problems in the future.  Saves downloading the whole blockchain and if something goes wrong I have a quick backup.

If you have a new apollo II then is seems you must run the 2.0.7 because its designed to work with the new systems they produced.  My understanding is you can't go backwards to an older version with the new system.

A few things to try.

When it says "connection refused" it means the bitcoind program stopped running.  Back a few messages, I recommend a way to monitor your node in real time with live scrolling of the debug.log.  It's very important to monitor that log as it tells you how the download is going with the database.
Sometimes you can just restart the node and it will pick up where it left off.  If you click on the button multiple times trying to force restart it can crash bitcoind.   

having a running log window open allows you to see the progress and see how it stopped.  Did it just crash or did it exit or close.  you can see that in the logs.

Having the miner running may stress the power supply and for some reason the cpu is sensitive to power spikes.   that can cause a crash.  open the system monitor so you can see how busy the cpu is when downloading the blocks.  It's not a simple download, it decrypts it which takes cpu power and sets up the database.   In system monitor you can also see if bitcoind is running or not and how much resources it is taking up.

I have my unit on backup power with line conditioners.  Also only running the IBD"Initial Blockchain Download" is best.  don't have multiple browsers open and really, don't mine until it's complete.  bitcoind will use a lot of memory when downloading. 

Once the download is complete I can tell you that the system runs pretty well.  In eco, normal, or turbo, depending on your temp and noise preference.

I had problems with my microsd card that i changed out and i got two of those and also 2 pcie cards.  Once the IBD is complete I made a backup of the blockchain on the second pcie in case i had problems in the future.  Saves downloading the whole blockchain and if something goes wrong I have a quick backup.

If you have a new apollo II then is seems you must run the 2.0.7 because its designed to work with the new systems they produced.  My understanding is you can't go backwards to an older version with the new system.