I am only working on the base plugin WPML compatibility at the moment. There appears to be a number of challenges to getting WPML to work properly; at least when using the documentation they provide. I’ve sent them a detailed description of the technical issues and am awaiting a reply.
Only Power, Experience, and Premier will be updated at some point in the future to be WPML compatible. It is far too much work jumping through WPML technical hoops to go back and port all the older add on packs.
In the meantime the latest SLP 4.5.07 prerelease is available for free from the SLP website:
https://wp.storelocatorplus.com/product/store-locator-plus-prerelease/
Also read this:
https://docs.storelocatorplus.com/blog/using-language-files-to-help-wpml-with-gettext/
Short version: You must have a complete language file for your alternate languages presented on your website front-end with WPML. If your site is in English and you want to provide Spanish translations for things like “no results found” you must create a Spanish version of your page with the [slplus] shortcode AND make sure the Spanish language files are up-to-date with the latest version. I use Loco Translate to first Sync and then use Google Translate to fill in any missing translations.
Once WPML starts answering some of my half-dozen technical questions I can start working on more complext issues.
Currently SLP 4.5.07-beta-02 appears to be changing the UI elements of the base plugin such as the radius drop down entries (“10 miles” to “10 millas” for example) and the Find Locations default text on the find button.
4.5.07-beta-03 (not out yet) will also tell Google which language is being used to view the page with the [slplus] code and will change the Google Map Elements (“satellite/map” and copyright and town names) to match the selected language.
Still waiting to hear back from WPML on how to make things like user-settable labels like “Search Labels (Experience / Search / Search Labels)” settings like the Address Label and Radius Label translate on-the-fly without incurring the TRIPLE execution speed performance hit (it is 3x slower loading the page if I use their register/translate string filters).
Please test and give feedback based on translation issues with the base plugin. I’m planning to publish an updated WPML friendly release of the base plugin version 4.5.07 production by Sunday AM.