this is a common issue some merchants have faced in the past as well. here are some things you can try:
un-verify and remove your current GSC property. leave it as is for some days and then try again.
change your sitemap a bit, let’s say by adding a new product or collection, and then re-submit it.
submit sub-sitemaps.
change your verification method. so if it is currently HTML, you can change it to DNS or something. then try to re-submit your sitemap.
further, ask shopify to verify their logs and if the sitemap is being correctly processed by googlebots.
maybe try and create a human sitemap page where you can simply use a screamingfrog crawl, list all the internal links, and ask google to crawl your pages.
check for robots or sitemap redirection issues too.
you can try implementing some points from above. most importantly, merchants in the past mentioned that they had to wait before google discovered their pages. so be patient.