If you are unable to select text on a page in the online reader, either for highlighting text or copying it, or if the full text search isn't returning any results even though you are sure the search word exists within the text then the likely issue is that the original ebook file we used to create the online reader file is a PDF that is missing it's text layer.
Please complete our support form to submit a ticket to our customer support. If you mention which ebook is affected, we can then contact the publisher to request they resubmit that ebook with the text layer in place. If the ebook is also available in EPUB format we can use the EPUB to create an online reader file that will fix the missing functionality while we wait for a corrected PDF.
If the ebook is old, or was created by scanning the printed physical book then unfortunately it may not be possible to obtain a corrected ebook file.