1) Make following changes in .htaccess

[0] Fix | Delete

RewriteBase [[relativeurl_]]

[1] Fix | Delete

It is mentioned in installer and on installation document

[2] Fix | Delete

2) Please check if new language is added in /application/language then update install.xml

[3] Fix | Delete

3) Follow the upgrade guide here :

[4] Fix | Delete

https://wiki.invoiceplane.com/en/1.6/getting-started/updating-ip

[5] Fix | Delete

4)PHP REQUIREMENT LINK : https://wiki.invoiceplane.com/en/1.6/getting-started/requirements

[6] Fix | Delete

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.

[7] Fix | Delete