Exporting epub from Indesign CC 2017, will not open in Adobe Digital Editions 4.5

Hello,

We have created a booklet that is 196 pages, and successfully exported it as a press-ready pdf for printing and interactive pdf for online viewing. Our client has asked for it in an epub format.  We have exported test files and they open and are navigable in both iBooks and Microsoft Edge, but will not open in Adobe Digital Editions on a PC. We get no error message, but the twirling blue circle never stops until you quit the program.

We have tried numerous options and looked at many forum answers, and still can't get this to work.  We have removed the TOC, removed all hyperlinks, made a new TOC for epub- again, all open in iBooks and Edge but not ADE. We have also tried exporting other brochures to epub and they will not open in ADE. If this is an ADE setting, we can fix it and send a tutorial for our client's customers, but we are really searching for some answers that will not require this. Our client's customers are PC-based.

Any solutions are greatly appreciated, and thanks in advance for your help.