Server : Apache System : Linux server1.cgrithy.com 3.10.0-1160.95.1.el7.x86_64 #1 SMP Mon Jul 24 13:59:37 UTC 2023 x86_64 User : nobody ( 99) PHP Version : 8.1.23 Disable Function : NONE Directory :  /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.