Support for Multisampled Textures Failed because HTML5 has no support for MSAA in Unreal Engine up to version 4.23. This may result in error while you try to launch project for Chrome or Firefox. Also same problem appears after packaged to HTML5, even if process ended up successfully.
What is Multisampling?
Multisampling, also known as multisample antialiasing (MSAA), is one method for achieving full-screen antialiasing (FSAA). With multisampling, each pixel at the edge of a polygon is sampled multiple times. For each sample-pass, a slight offset is applied to all screen coordinates. This offset is smaller than the actual size of the pixels. By averaging all these samples, the result is a smoother transition of the colors at the edges. Unlike supersampling (SSAA) which can result in the same pixel being shaded multiple times per pixel, multisampling runs the fragment program just once per pixel rasterized. However with MSAA multiple depth/stencil comparisons are performed per sample, one for each of the subsamples, which gives you sub-pixel spatial precision on your geometry and nice, smoothed edges on your polygons.khronos
This Error message appears in packaged and also in launch projects.
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Reason and Solution
Unfortunately HTML5 has no support for MSSA at the time being in UE4 and Multisampled Textures Failed may occur. Your solution is to avoid using MSAA in your project. Go to Project Settings >> Engine – Rendering >> Mobile MSAA set to No MSAA.