403 forbidden error with wordpress installed on sub folder

Hello

I am trying to access the https://pelbox.com/sitemapindex.xml file but it is giving me 403 forbidden error. The text version (actual xml only extension changed) of https://pelbox.com/sitemap.txt site works fine and I am able to open the file. I think it is something to do with .htaccess file but I don’t know what. Please help me. I am using this plugin to generate site maps

Thanks

https://www.ads-software.com/extend/plugins/bwp-google-xml-sitemaps/