The software for the Fujitsu S1500 scanners is 32 bit stuff and won’t work any longer with Catalina. But don’t throw your scanner away.
Instead get or update VueScan by Hamrick Software.
It works perfectly in either single sided or duplex mode.
I’m thankful for VueScan, which I’ve had for years to do better scanning with flatbed scanners. I’m thankful they saw fit to save our S1500 scanners from extinction.
I had set up a VM running Mojave in Parallels just so I could run that scanner. But I might as well keep the VM. You never know what other 32 bit apps I might run into.