Server : Apache System : Linux host44.registrar-servers.com 4.18.0-513.18.1.lve.2.el8.x86_64 #1 SMP Sat Mar 30 15:36:11 UTC 2024 x86_64 User : vapecompany ( 2719) PHP Version : 7.4.33 Disable Function : NONE Directory :  /proc/self/root/var/softaculous/invoice/

Upload File : current_dir [ Writeable ] document_root [ Writeable ]

1) Make following changes in .htaccess 
RewriteBase [[relativeurl_]]
It is mentioned in installer and on installation document
2) Please check if new language is added in /application/language then update install.xml
3) Follow the upgrade guide here :
https://wiki.invoiceplane.com/en/1.6/getting-started/updating-ip
4)PHP REQUIREMENT LINK : https://wiki.invoiceplane.com/en/1.6/getting-started/requirements
5) We have kept min PHP version to 8.1 because composer.json states the same. Also we have removed mcrypt and xmlrpc extentions as these are moved to PECL library.