Hi!

I have installed mono-complete already. It is installed already.

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(base) kings@kings-MS-7C82:~/SMath$ sudo apt-get install mono-devel mono-complete
[sudo] password for kings:
Reading package lists... Done
Building dependency tree
Reading state information... Done
mono-complete is already the newest version (4.6.2.7+dfsg-1ubuntu1).
mono-devel is already the newest version (4.6.2.7+dfsg-1ubuntu1).
The following package was automatically installed and is no longer required:
linux-hwe-5.4-headers-5.4.0-42
Use 'sudo apt autoremove' to remove it.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

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Then I extracted the latest Smath Mono version( "SMathStudioDesktop.0_99_7822.Mono.tar.gz" archive files to the new empty directory on the Ubuntu OS.
The information of my Ubuntu OS is as follows;

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(base) kings@kings-MS-7C82:~/SMath$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.5 LTS
Release: 18.04
Codename: bionic

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SMath could not be started normally by following errors (Please refer to the file attached for full error list.)

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...
Could not load signature of TextRegionUtilities.SearchAndReplace:FocusWriterRegion due to: Could not load file or assembly or one of its dependencies. assembly:WriterRegion, Version=0.20.6984.23246, Culture=neutral, PublicKeyToken=null type:<unknown type> member:<none
SMath_err01_echoed.txt (24kb) downloaded 17 time(s).
....

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Please, guide me to fix this error!

Thank you!

David

Dear Mr. Carpl,

Thank you for your advice. Here are my reports.

1. After deleting the 9F5E37D-83F5-4A4B-A106-0BA7B202ABBB directory, SMath is still failed to run.
2. After deleting the whole ~/.config/SMathn directory it could start normally

3. But trying to install the plugin, "Text Region Utilities", the program crashed, and then the SMath program could be lunched.

Regards,

David