Hello,

We do not officially support 2015 version any more but I can provide some general information.

This error usually is caused by version mismatch so the first thing you will need to do is to clean up the DLLs to make sure you use only one version. You can follow these steps:

1. Find out what version you are currently installed on your system. The default location is C:\Program Files\Essential Objects\EO.Total xxxx), where "xxxx" is the product version. Note that on 64 bit system, replace "Program Files" with "Program Files (x86)";
2. Delete all your EO.Web.dll and EO.Web.licx files. If you do not have access to the original files, back them up to a separate folder;
3. Update your project reference to use EO.Web.dll and EO.Base.dll from the folder in step 1;
4. Restart Visual Studio and rebuild your project;

Usually this would take care of the error. Once the error is gone, you can log into your account (or ask whoever purchased the license originally to log into his/her account) to download a matching license file/key. Make sure the license version match the DLL version ---- each version uses a different license key and you may have access to license keys for multiple versions, so make sure you use the right one.

If you still have problem, then please PM us your order number (or license key content) and we will check whether your maintenance is still active. The maintenance covers new versions and tech support. When you place the order, we automatically includes maintenance for one year. After that you will need to renew it in order to continue receive tech support (as well as receiving newer versions). So if you have not renewed your maintenance plan, then you may wish to consider renewing it or purchasing a new license (depending on which one is cheaper since renewing price depends on how old your version is and it can be more expensive than buying a new license). That way you will both be able to continue receiving tech support and updating to the current version.

Hope this helps.

Thanks!