Membership Request Webpart error after enabling Anonymous Access

After a successful deploy and months of using solution without issue, the need arose to allow anonymous user access to a list on the web application running FBA User Pack for SP13.

Since anonymous user access has been turned on, the Membership Request webpart is unable to add users to database. The error message i receive is "An unexpected error has occurred. Please contact your administrator if this problem persists, or check the SharePoint log file for more details." (Sharepoint log files show no real indication of error)

In FBA Site Configuration settings, i have "Review Membership Requests" unchecked. When it is checked, the membership request webpart creates a list item in the Membership Review List however, when editing the item to "Approved" nothing happens.

I am still able to add users via FBA User Management. All other webparts work as expected.

Any help would be appreciated.
The membership request web part should work fine for you with anonymous access, as well as editing the item to "approved" (when editing to approved, the user should get an approval email and the user will be removed from the membership review list. You may have to refresh the page to see the user removed, as it hasn't always happened before the page is refreshed).

As for the error message, I really need more information, which will be in the SharePoint log file. Right after the error occurs, check your log file starting with the most recent entries and search up. You should be able to search for "FBA" or "Unexpected" to find the error.
After reviewing the ULS logs, here are some errors i get:

Error 1:
System.Xml.Xsl.XslLoadException: XSLT compile error. An error occurred
at (32,11). ---> System.Xml.XmlException: The 'p' start tag on line 16 position 13 does not match the end tag of 'div'. Line 32, position 11.
at System.Xml.XmlTextReaderImpl.Throw(String res, String[] args)
at System.Xml.XmlTextReaderImpl.ThrowTagMismatch(NodeData startTag)
at System.Xml.XmlTextReaderImpl.ParseEndElement()
at System.Xml.XmlTextReaderImpl.ParseElementContent()
at System.Xml.Xsl.Xslt.XsltInput.ReadTextNodes()
at System.Xml.Xsl.Xslt.XsltInput.ReadNextSibling()
at System.Xml.Xsl.Xslt.XsltLoader.LoadInstructions(List1 content, InstructionFlags flags)
at System.Xml.Xsl.Xslt.XsltLoader.LoadLiteralResultElement(Boolean asStylesheet)
at System.Xml.Xsl.Xslt.XsltLoader.LoadInstructions(List
1 content, InstructionFlags flags)
at System.Xml.Xsl.Xslt.XsltLoader.LoadLiteralResultElement(Boolean asStylesheet)
at System.Xml.Xsl.Xslt.XsltLoader.LoadInstructions(List1 content, InstructionFlags flags)
at System.Xml.Xsl.Xslt.XsltLoader.LoadLiteralResultElement(Boolean asStylesheet)
at System.Xml.Xsl.Xslt.XsltLoader.LoadInstructions(List
1 content, InstructionFlags flags)
at System.Xml.Xsl.Xslt.XsltLoader.LoadLiteralResultElement(Boolean asStylesheet)
at System.Xml.Xsl.Xslt.XsltLoader.LoadInstructions(List`1 content, InstructionFlags flags)
at System.Xml.Xsl.Xslt.XsltLoader.LoadTemplate(NsDecl stylesheetNsList)
at System.Xml.Xsl.Xslt.XsltLoader.LoadRealStylesheet()
at System.Xml.Xsl.Xslt.XsltLoader.LoadDocument()
at System.Xml.Xsl.Xslt.XsltLoader.LoadStylesheet(XmlReader reader, Boolean include) -
-- End of inner exception stack trace ---
at System.Xml.Xsl.Xslt.XsltLoader.LoadStylesheet(XmlReader reader, Boolean include)
at System.Xml.Xsl.Xslt.XsltLoader.Load(Compiler compiler, Object stylesheet, XmlResolver xmlResolver)
at System.Xml.Xsl.Xslt.Compiler.Compile(Object stylesheet, XmlResolver xmlResolver, QilExpression& qil)
at System.Xml.Xsl.XslCompiledTransform.LoadInternal(Object stylesheet, XsltSettings settings, XmlResolver stylesheetResolver)
at Visigo.Sharepoint.FormsBasedAuthentication.Email.SendEmail(SPWeb web, String emailTo, String xslt, IDictionary xslValues)

Error 2:
SendEmail failed
It looks like the template has been customized and there's an error in the customized template. You can get the default templates from the resource file:

https://sharepoint2013fba.codeplex.com/SourceControl/latest#Visigo.Sharepoint.FormsBasedAuthentication/Visigo.Sharepoint.FormsBasedAuthentication/ResourcesAppGlobal/FBAPackWebPages.resx
Looks like it was a missing tag in the site configuration settings. All is better in the world now. Thanks for your help!