can’t apply one design to many listings simultaneously. only way to do it - is selecting and applying one by one.
I just tried it here but it worked like a charm. Did you select all listings in overview mode before opening the Design popover? You can also right-click in Overview mode and choose “select all”.
yes, selected all at the left first and the select them again in preview (this is strange for me to double select each time i want to mass process something). triple checked this.
and this problem appeared today for the first time (B45) when i imported new batch from my ebay. previously with B44 i have no such problem.
delete those listings and import them again. working.