You need to rebuild the database using -reindex to go back to unpruned mode. This will redownload the entire blockchain.
To use the node without pruning you need to reindex your node. Is there a reason you need to use bitcoin core without being pruned though, bisq has its own built in wallets?
If you do, you'll have to start bitcoin core with the -reindex command (im not too familiar with macos but if you can run things from the console just run it with - reindex after it and it should reindex - the download might take a long time though and bitcoin's blockchain is over 200gb now (check you have the space first).
Thanks for taking the time to reply. As one who doesn't code I don't know how to use the -reindex command...
I assume that I open Terminal (MacOS), however what command line needs to be ahead of this -reindex command?
I've tried "dBs-MacBook-Pro:~ db$ /Volumes/Extreme\ Pro/Bitcoin/bitcoin.conf -reindex" but nothing seems to happen.
My issue is that Bitcoin Core doesn't open at all & shuts down when it says it needs to reindex
Fortunaltely I don't have a Space nor Bandwidth/Speed issues...
Cheers