I'm getting the following error on a number of my machines:

5/16/2017 9:07:29 AM | Enigma@Home | Message from server: Your app_info.xml file doesn't have a usable version of Enigma AV.

Same here. I'm using the optimized app I found here, might that be the cause?

yes

I am getting this on linux machines that can't even run Enigma AV.

@TJM, could you provide updated app_info.xml template for these cases?
*Platforms that can't run Enigma AV
*Windows so that we can use optimized apps parallel with Enigma AV

I'm getting the following error on a number of my machines:

5/16/2017 9:07:29 AM | Enigma@Home | Message from server: Your app_info.xml file doesn't have a usable version of Enigma AV.

Try adding the following to your app_info.xml file:

<app>
    <name>enigma_m4_3</name>
    <user_friendly_name>Enigma AV</user_friendly_name>
    <non_cpu_intensive>0</non_cpu_intensive>
</app>
<file_info>
    <name>wrapper_1.04_windows_intelx86.exe</name>
    <executable/>
</file_info>
<file_info>
    <name>enigma3_1.04_windows_intelx86.exe</name>
    <executable/>
</file_info>
<file_info>
    <name>job_1.49.xml</name>
</file_info>
<app_version>
    <app_name>enigma_m4_3</app_name>
    <version_num>104</version_num>
    <avg_ncpus>1.000000</avg_ncpus>
    <max_ncpus>1.000000</max_ncpus>
    <flops>8478211443.746548</flops>
    <api_version>6.11.4</api_version>
    <file_ref>
        <file_name>wrapper_1.04_windows_intelx86.exe</file_name>
        <open_name>enigma3_wrapper.exe</open_name>
        <main_program/>
        <copy_file/>
    </file_ref>
    <file_ref>
        <file_name>enigma3_1.04_windows_intelx86.exe</file_name>
        <open_name>enigma_av.exe</open_name>
        <copy_file/>
    </file_ref>
    <file_ref>
        <file_name>job_1.49.xml</file_name>
        <open_name>job.xml</open_name>
        <copy_file/>
    </file_ref>
</app_version>

Note: The flops will need to be adjusted to get accurate estimates, as each machine is different.

If the client does not automatically download the 3 files, here are the links:

http://download.enigmaathome.net/wrapper_1.04_windows_intelx86.exe
File size: 510976 Bytes MD5: e87d9fce360a9f1005471859c5367c8d

http://download.enigmaathome.net/enigma3_1.04_windows_intelx86.exe
File size: 51200 Bytes MD5: c7d3e0074757f44d14cb879121c645d0

http://download.enigmaathome.net/job_1.49.xml
File size: 179 Bytes MD5: 168ddfa32a87dfb96c7d83561681f140

Albeit not changing anything, I don't get this error anymore - but still get no work either:

20.05.2017 13:52:28 | Enigma@Home | update requested by user
20.05.2017 13:52:32 | Enigma@Home | Sending scheduler request: Requested by user.
20.05.2017 13:52:32 | Enigma@Home | Not requesting tasks: don't need (CPU: job cache full; Intel GPU: )
20.05.2017 13:52:33 | Enigma@Home | Scheduler request completed

Detaching and re-ataching got me the AV 1.05 app. Works fine (faster than ever, actually).