make sure:

- you refresh your browser
- you have installed the system plugin

Yes I refreshed the browser - cleaned up cache - but used older version of system plugin. In the meantime rolled back to backup of the website. After this installed system pligin 1.0.2 and tried to install the component 3.1.1. after which I get the error:
Waarschuwing
JInstaller: :Installeren: Fout SQL Duplicate entry '1' for key 'PRIMARY'
Extensie Updaten: SQL fout verwerken zoekopdracht: DB functie is mislukt met het volgende foutnummer 1062
Duplicate entry '1' for key 'PRIMARY'
SQL =
INSERT INTO `#__invoices_currencies` (`id`, `currency_symbol`, `currency_code`, `currency_format`, `currency_name`, `currency_published`, `currency_rate`, `currency_locale`, `currency_displayed`, `currency_perc.... etc etc etc - see attachment
Going to invoice manager leads me to the same version as in previous attachment.

yes, now when trying to upgrade it tries to reinstall that DB table. you can empty the currencies table if you want and try again..

Still no luck. Tried with deleting the colomn but after that I got another duplicate error - went back to backup and installed first te component and after this the plugin - this went well. But I am back at the beginning as the component is still not working and same screenshot as first. In console see some errors regarding vue.js but not sure if this has to do with the component not working.

please, send me access and I'll take a look.

I'm having the same error any idea how to fix this?