Did your new tires mount as difficult as the first? If so, maybe build up the bed with a layer or two of tubeless tape for more bead interference. This worked for me until I decided the advantages of tubeless do not warrant the extra work, at least not for me.
If you plan to swap tubeless tires often then consider the skinny stripper product ( yes, they are called that, look for them on the fatty stripper website). The layer of the stripper adds to the interference and aids in creating a seal. Also makes tire changes back and forth cleaner. I ran them while running tubeless after a while. They were a bit of a pain to set up initially, but in the long run make sense to me.