My sad story:
I have an emonPi and emonTX (wanting to add a second one I purchased a few years back not yet commissioned) reading different lines usage and PV production.
I can still access the Setup page and the log shows continuous updates but no info is shown on the dashboards.
Yes, if you buy a new SD can install a fresh copy of EmonCMS/SD on that, then put the old SD card into a USB reader, and plug that you your Pi. On booting the Pi you will have afresh install of EmonCMS on the new card, with the option under the Admin menu to import all the old data, setttings, and dashboards from from the old SD card in the USB reader. It works great!
The only thing to bear in mind is if you installed anything else, like NodeRed, that won’t be on the new installation, you’ll have to apply that manually.