I have A Imac Pro and I can back up my iMac Pro to my time machine but I can't back up my Ima

I have a Time Machine I set it up and at this time my wifi work and when I backup my Mac Book Pro I can back up my files to my Time Machine.

But when I want to back my Imac to my Time Machine I can't. I go to the Time Machine Icon the screen comes up I click on use this disk and I get serching for diskt runs for 3 minutes then I get a popup message ( The backup Disk Image "/Volumes/WilliamJPajerski Time -2/IMAC WilliamJPajerski's (2).Spacebundlr couldnot be assed (error-1)

can you help 😢