You can always check the validity and details of your e-vignette in the web portal, simply select the country of the vehicle registration and enter it's licence plate number here.
Of course you may also contact us and we will be happy to assist you.
Related articles:
Does the Slovak e-vignette activate immediately?
How long is the Slovak e-vignette valid?
Do I get a confirmation email for my Slovak e-vignette order?
Vignetteslovakia.com contact information
Slovak National Motorway Company (NDS) contact information (Slovak authority)