Getting no results with Solr 7.5

[joebassi]

I have solr-magento1 extension set up on Magento 1.9.3.9 and configured properly and all the backend tests are fine. But when I search on the frontend, I get zero results, I have everything indexed.
Backend:
Solr Module is activated.
Solr server configuration is complete.
Connection to Solr server established successfully.
Test search request issued successfully.
Module version: 1.7.6
Library version: 3.0.0
Magento version: 1.9.3.9 (Community Edition)
Solr version: 7.5.0
Solr: /solr/core2/select?fl=name_t,name_s,description_t_mv&q=:&rows=1
solr.log

{
"responseHeader":{
"status":0,
"QTime":0,
"params":{
"q":":",
"fl":"name_t,name_s,description_t_mv",
"rows":"1",
"_":"1539720495417"}},
"response":{"numFound":1080,"start":0,"docs":[
{
"description_t_mv":["9.7-oz, 100% combed and ring spun cotton\nSuper soft 30 single 1x1 baby rib knit\nSide seamed\nContoured fit"],
"name_t":"DISCONTINUED BELLA+CANVAS® BABY RIB SHORT SLEEVE V-NECK LADIES' TEE. 1005",
"name_s":"DISCONTINUED BELLA+CANVAS® BABY RIB SHORT SLEEVE V-NECK LADIES' TEE. 1005"}]
}}

[xyphoid]

I had to switch to solr 6.6.5 + java 8 as per the listed requirements to get this working - I tried 7.5 first too but the provided solr configuration isn't compatible with that.