Unlike previous versions (v3, v4), P3Dv5 has specific requirements:

Tip: Always check for a “v5” or “v5.4” installer. Addons designed for v4.5 are often not compatible without modded DLLs.

P3Dv5 took a massive leap forward by introducing TrueSKY and HDR lighting, but it can still look flat out of the box.

You don't need to spend $1,000. Here are essential freebies: