Images from second row down are blacked out

I embedded a photo gallery poll on our website. The voting form shows up perfectly on pollunit.com, but on our website the bottom thumbnails are black… When you click the black thumbnail, the right image does appear in the pop-up.

Did I do something wrong with setting up the iframe?

Thanks in advance.

Hello Lies, could you share the linkt to the embedding page? If it is a hidden / secret page, you could send the link to support@pollunit.com.
And please let us know what operating system and browser (incl. version) you are using.

Closed as fixed